I think my biggest in game mistake is turning out to be maxing a second Wu Kong. I’m currently using him in Alliance Wars, but he’s the only hero I’ve got 2 of maxed. I fed 1 or 2 more Wu, but they went to Delilah, who was the first 5* I got. I am completely fine with that.
I’m holding a bunch of 4* duplicates just in case I get to the point I have nothing better to work on. However, I might start holding off pulling feeder heroes totally, as my list of unique heroes is very slim once I get past those I’m working on currently.
I also hold on trainers to use only on 3rd or 4th chevron, unless it’s a 1* trainer. I am finding that food is not remotely a problem for me, yet I still do it to save on food costs.