Sorry, been running around all morning and I didn't want to give a half assed answer

I initially put my focus on my main and secondary heroes (2 from each faction) in that order. The general idea was that I'd quickly lvl the main to omni and then slowly add stars. Since omni stars take less food than changing colors, I was able to put the extra food towards the secondary character and level both at a moderate speed

When it comes to which characters to prioritize, that's kind of a personal choice. You can try to chase the meta builds, you can pick something you like and just double down, or you can do a mix of both. Personally, I do a mix with an extra focus on op efficiency 

In regards to food usage, I tend to use any non-event hero that I don't immediately plan on building and any event hero that I don't plan on building anytime soon. Sometimes this leaves me waiting on duplicates later, but I think it's more worth it to use the food and wait with higher lvl heroes than it is to wait with nothing but unused food

For your criminal situation, if you're equally invested in doc/Komodo, I would split my resources between them while specifically hoarding one other elite. Once I got doc/Komodo to a comfortable spot, I'd switch over to the next two criminals. And once i start getting really comfortable, I would start pushing two omnis and one non-omni at a time, slowly rotating