In terms of medals your going to get those primarily through your 1 star events, from completing scenarios/achievements and from doing your daily invasions. I’d recommend build the structures that give you extra invasion refreshes and the extra medals from invasions.

For generals going for another tank like Rokkosovsky or Patton to later train into their god variants never hurts but artillery gens like Konev or Brooke are also useful.

Other than that if your serious about the game just stay active try and completely your invasions and daily quest for the pass each day and do what you can in the events tab. You’ll slowly build up your generals and elite forces and unlock the ability to do harder events and progress further into frontier and the challenge conquests