Aife is the ONLY one you should eat.
It looks as though you’ve already started eating your 3* heroes based on the fact that Bane seems to be your only leveled 3*. Don’t eat any more 3*s.
As you’re finding out, it take a lot of effort to level 4s and even more to level 5s I would highly recommend you pause leveling the 4* and 5s until you have a solid 3 team. The consequence to starting with 4* and 5* leveling is that it sucks up all your levelling resources and you’re going to get to a point where you have a hard time getting the ascention materials you’ll need. A fully ascended 3* is superior to a 1st or even 2nd level 4*.
Bane, Karil, Azar is a good start. Belith, Brienne, Berden, Hawkmoon, Balthazar, Tyrum, and Valen are 3*'s you’ll want to keep an eye out for. Look up the “best 3* heroes” thread on this forum and read it.
Only use 1* and 2* heroes to feed until you have a better understanding of what your team needs. There’s no multiplier for feeding 10 at a time. In fact, the suggestion is to feed the 3* heroes one like color feeder at a time - this gives them the best chance of maxing their special skill by the time they’re 3/50 (yes, even though the skill-up is only 1-2%).