I will try to Show how it worked out for me.
My 5 first 4* heroes were Kiril, Chao, Tiburtus, Little John and Boril.
I was stuck with them for quite some time so I developed the following startegy.
I exclusively attacked red tanks , AoE heroes were a plus, Riposte hero were a no go, stuppid positioning and color choice of heroes were a plus.
So yes I spent some food on rerolls but all in all it worked quite well.
Look at what you have. Look what your opponents have and make the best of it.
If you are very unlucky and have 0 synergy with your 4* heroes emblem up some 3*'s and fill the gaps.
Good luck with your further summonings.