Strange thing, there is no single topic about this, there is, thought, a topic about weakest strategy.
So, main question is - your favorite strategy, but, it's not so easy, as strategy can be varied, to suit your game location and needs.
More proper is to answer this question
"What strategy do you mostly prefer"
For me, it have to be Perfect Defence, for a reason, that myself here is mostly defencive player (and I know it is my weakness), so perfect defense give me cheap and tough defense.
Sometimes it can be "Imperialist" on maps, such as Africa, where you simply don't have any coin, to support 2 tanks at the same time.
All others I tend not to use, unless I am trying new (unsuccessful) approaches
PS. just now finished another game, it seems like defense is not so perfect after all.
At least versus Blitz. I kept loosing my troops with disadvantage in offence, so it's -/-