Noob Training Series

[Imp]

For learnimg the basic mechanics of the game I would say generated battles are far better.
You know exactly what needs to be achieved
You can decide the units involved incluing if you wish setting the AI side to human buy,
This way you can add layers as you become proficient.
Say infantry only to start
Then add bunkers, artillery, APCs, tanks, air & air defence etc.

For example want to learn how to use infantry vs tanks, buy the units that let you do that.
You can also pick your map to learn how to operate in diffrent terrain from urban to dessert.