Perhaps others will disagree, as I'm no expert nor one of the highest level players here (currently 150 IA), but I've narrowed down my troop selection to the following:
War army: rifles, tanks, healing trucks, cannons, planes
For my raiding army, I replace most of my cannons with heavy infantry for faster build times and quick food runs.
I never use raiders, miners, mortars, or anything from the factory, as I don't feel their value matches their troop space/training time. Everybody has their own style, of course, but I've found this mix works very well for me. I typically attack players 15 to 25 levels ahead of me in war and generally succeed. It also simplifies my upgrade tree, as I can focus on a relatively small subset.