If you use all the free money you get at the early levels, it's easy to unlock all the heroes, but then you're left with super slow progression for getting actual star cards for all those heroes you just unlocked as well as the troopers, reinforcements, and starships.

Personally, I tried out all the heroes in arcade first, picked my favourite ones that were locked, and only bought them (in my case, Iden and Leia). I don't really even play heroes that much in the first place. I have more fun playing as the reinforcements, mainly the Aerial class. All my crafting parts have gone towards maxing out my Jet Troopers with Tier 4 cards.