I'd like to learn the game, but there's just too much stuff going on too fast. And since I'm new to the game it's almost impossible for me to grasp it.

Is there like a tutorial to it or even better gamemode VS AI only with unlimited time between my rounds?

That or at least suggest me a team composition i should go hard for, so that I know what to buy/upgrade at least, because there's so much more like items and other stuff that just make the game so much more intimidating for me.