My first advice would be to look @ the heros in the tavern you will notice they all have Command, Strength and intelligence listed. The minimum seems to be 60 under each category. They higher you can get @ the start the more it will go up with the runes, gems and whatever research brings those numbers up
My other piece of advice would be to try and work on active heros only in the Blacksmith. All power earned goes toward your total power. But if you are working on inactive heros then that is basically unused power as you can only use 5 heros @ a time.
Heros should have a good mix and not just swords and archers or just mages. 2 mages max is recommended. Work on powering them up in both the blacksmith and talent.
Save some credits for big ticket heros in tavern. Don't just recruit small heros because there may be a limit on how many can be stored (that has not been proven yet, but to be safe keep that possibility in mind)
