Typically there is no "best tactic". It is all up to you and direction the where you want to go.

Generally, most players or the players who have the experience typically go barracks then infra in core cities while researching infantry and armored cars at the same time.

In the research tree there may be different ways you want to go some go light tanks or planes, others go with the ships. There is a mix of things as well.

But beware of your economy and you should adjust your economy based on the strategy you want to go.

You also need to be able to reach out ties to other nations and players, look for the closest ones around you.

Here is a quick guide for you: goo.gl/h33qsK

Good luck and have fun!