I’m too busy for joining a game but still have limited spare time. To save myself from boredom, I’m sharing some ideas of mine so you guys can criticise me. I don’t think this can be qualified as a guide but I’m still cheeky enough to put it here. Make sure your comments below can turn this useless thread into a useful guide.
Take notice that this thread isn’t going to show what to do in a specific game. What to do in a specific game depends on the situation.
I’ll divide the skills that make a good COW player into 3 categories: Military, Economy and Diplomacy.
Their relationships:
Economy to military: The strength of your army is related to the amount of resources you can use to produce, upgrade and research.
Economy to diplomacy: You can use resources to bribe others. Good players also measure your competence up based on your economy in additional to combat skill.
Diplomacy to military: By this way you can avoid getting sandwiched and take your neighbours out one by one. You can also be-friend with good players.
Military to economy: By conquering more provinces, your resources production increase.
Military to diplomacy: Nobody wants to upset a skilful player who has the most VPs and the largest army, right?
To be continued…

Most contents following will be very basic.
Economy
Ignore those things like GDP. The sole indicator of a country’s economy is its resources production rate.
Here are the types of resources in COW:
1. Goods: needed for researches, ordnance, infantry and planes
2. Food: needed for infantry, ships and ordnance
3. Steel: needed for ordnance, tanks, ships and industries
4. Oil: needed for ‘mobile’ units(tanks, mot. and mech. inf., SPAA and SParty), planes ,ships and industries
5. Rares: Needed for industries and planes
Others:
Cash: needed in a small amount for every research, production and construction. The extra cash can be used in stock market or espionage
MP: needed for production of every units
Look at a game you’re currently playing. Below the resources currently in stock, there’s an hourly resources production rate of your country. To compare with other countries, you can open the newspaper. The statistic ‘the largest economies’ is revealed every 4 days, starting from day2. The number there is the sum of your country’s daily production of goods, rares, food, steel and oil.
Factors affecting the production rate of resources:
The standard daily production of resources in a city:
Cash 6000
MP 600
The mains 6000
Rural provinces producing resources
Cash 900
MP 150
The mains 1500
To be continued(It might take weeks for me to finish this)

rural provinces not producing resources: cash: 600 mp:450
The actual production will be affected by these factors: 1. core and non-core 2. morale 3. industries 4. Daily cost
Non-core provinces mean the ones you conquer from others and colonies in the case of HWW. Non-core provinces produce only 25% of the resources produced in core ones.
Resource production is calculated by: standard x morale%. Morale increases when you’re winning against others, capture capitals(10%) and it drops when you’re at war with others(max. 25%, 5% for each country), losing a war lacking resources(<0 production rate) or simply have a large empire(expansion).
Urban industries(max. lv.5) increase your production to 200% of the original and rural ones(max. lv.3) increase it to 400% of the original.
Daily cost: every unit you produce consumes a small amount of resources. It is already deducted in the production rate
To be continued…

There are two ways to enlarge your economy
1. Industrialise
However, where to build?
Core vs. non-core
The resource production in non-core provinces is 75% less than core. As industries increase production by%, building in non-core provinces is 25% cost-effective comparing to core.You should only build them when you suspect a long game, your core is well-developed or you’re playing countries only playable in AÇAI.
City vs Local
How long it takes to get profit:
City: Local:
Lv.1 5.34 days 6.10 days
Lv.2 4.97 days 4.97 days
Lv.3 4.88 days 4.39 days
Lv.4 4.94 days
Lv.5 5.15 days

We can see that the cost-effectiveness of local industries are higher. But considering actual increase(+3000), urban industries are higher(+6000)(both at max.level)
Personally, I suggest to construct based on the following classifications:
With extra in stock even without industries: don't build any!
Will become short if other industries are maxed: build in a local province
A constantly used resource, but isn't in lacking because another important resource is lacked: build in two rural province or one with an urban industry of lv.3
Constantly used with only a city producing it: definitely lv.5!
You may notice that I avoid building in cities because you need to upgrade your production buildings there
To be continued...

2. Expanding
Conquered provinces can increase your production without much price(your army can be used again). Capitals also give you a 10% morale boost. However, if you can't conserve units well, this is not recommended. Focusing on expanding means you give up trying to use resources to build up economy, put all resources in military and boost your economy by expanding rapidly. In my opinion, conquering a playable country in the first 3game days.
Recruiting stations
No matter which method you chose above, recruiting stations is a must. If you choose to expand and are successful, you'll need to build RCs sooner.
I don't have the time to calculate, but I guess the efficiency assuming that in urban is 100%:
Rural: 75%
Rural(produce resources): 25%
Don't build in non-cores as well!

According to the above statistics, urban rcs are the most effective. however, again, you might be busy building production buildings in city, so you might not be able to catch up with your needs only building rcs in cities between gaps of production buildings upgrade.

Stock market
This is a place where you can sell and buy resources. The trades here are mostly expensive. You often only receive cash for the same amount as your resources and need 10 unit of cash to buy a unit of oil/steel.
However, I found good prices pop up at some fixed time. In my last game, to my luck, selling prices below 5 always appear the time I come online. Only buy resources at these times. And for selling resources, there are much fewer good prices, especially rares. Be alert that you shouldn't spend too much cash here. You need them for every other activities. Espionage is useful when used correctly.

Now, you have a handful of resources. But how to use them?

Research: A common mistake is to research all types of units. When I did that before, my reason was that you would then have the suitable units to face every situation. However, what if your opponent just spam a kind of unit, for instance , planes? You might have 4 lv.1 AA, 2 interceptors and 1SP one, but how can you stand against 50+ bombers? Therefore, you should just choose a few units which can synergize well
to be continued...

It’ll be even better if the units get a doctrine bonus
Axis: mot. inf. med. tank subs attack bombers
Allied: TD SParty mech inf. tac bomber destroyer
Comintern: arty/r arty med. tank attack bomber
Pan-Asian militia/inf. arty LT tac bomber battleships naval bombers
Concentrate on a few and upgrade them continuously, though you may need to estimate the number of units you need and take a balance between quantity and quality.
Construction
Don’t build more than one type of production building in a city. There’s only a production slot so any extra ones are wasting resources.
Upgrade them to get minimum production time.
Make use of buildings captured.
Build airstrips based on the range of your planes
Build propaganda offices when your cores’ morale drop below 100%
Build fortifications/bunkers only in a defensive war and in provinces where your troops get bonuses.
Ports are needed when there apis water separating two parts of your country.
Infrastructure gives your units a % speed boost, so you should build them, if units have to travel a long distance form production centres to the front a long time, in large provinces with plain terrain

Military
I want to explain the basic commands here cause I recently saw some player who played 84 games couldn’t move his units accurately.
Move: there are some black dots in provinces if you look close enough. These are key points for defending your provinces, capturing enemy provinces and making precise concentration of stacks
Attack: this function makes your units move towards the enemy units specified until they’re within attack range. Though recently artillery can’t use this function.
Split: you can separate units in a stack to execute their own orders
Forced march: units move 50% faster but their hp drops by 5% every hour(5% of full hp, I think), not recommended to use unless your units are at risk of getting destroyed unless they make a quick escape
Add army: a useful command that can make several units to move to the same place or attack the same stack. This can be done by the add army feature in mobile, press ctrl while selecting or long press the units

Patrol: your planes deal 50% of attack damage to enemy units in the patrol area every 15min.
Units statistics explanation
HP: no need
View range: units can spot enemy units/stack at this distance and closer. Though you can see two circles around your units: the first is the view range on the statistics and the other is the range you can know what exactly are these units and their states. If they've only entered the first circle, they'll appear as convoys/infantry regiment.

Speed: affected by terrain, you can check the terrain effect table below. All units are at their fastest speed on plains. But mobile units' speed drop in forest and hills, while others' speed remain unchanged. All units are the slowest in mountains.


Flight range(I forget how it's called): the largest distance a plane can operate from an airstrip or travel without refueling at an airstrip.

Armor class: every unit belong to an armor class. It decides their damage intake when in combat.

Thx.

Stealth: can’t be sighted by opponents unless it’s in a scout unit’s view range(of the same level)
Scout: detect stealth units of the same level or below
Melee Combat:
When units face enemy units when moving or are intended to attack units, they’re the attacker
When units idle and meet enemy units, they’re the defender.
When units of both sides are moving and they meet, they’re both the attacker and defender.
In every 30 min., the attacker deals attack damage according to the enemy’s armor class and receives defensive damage according to its own armour class.( the damage is affected by terrain as well)
When an Axis AC attacks an Axis inf. in a city, it deals 3.5 damage to inf. and receives 2.6 damage.
Units in melee combat CAN’T RETREAT, they fight until one of them is dead, make sure your units are strong enough to defeat units on the route

Melee combat between stacks
Each stack has its own armour class distribution(2 inf., 1 AC and 2 LT= unarmored 40%, light armoured 60%)
A stack's damage towards an armour class is calculated by the sum of the ten units dealing the highest damage to the armour class in it
The damage dealt to a specific armour class in a stack= Damage x armour class distribution
Total damage = the sum of damage received by each armour class

Damage efficiency: a unit's damage efficiency drops by 1 % when it misses 2 % of total health
Bombardment:
Ranged units can deal damage from a distance every 30 minutes according to their attack damage without taking losses
Warnings: When you're bombarding an AI stack with more than a unit, the AI will leave one behind and move the rest to attack you( in the case of land artillery), make sure to have meat shields, best to be in the same stack.
If the enemy has an artillery, it'll counter attack after your units enter its range for 3 min., assuming the player doesn't give any order to it.

I’m tired of this thread. I’m giving up.