Ally/Neutral benefit list
For Neutral priority, Abrahim should be the topmost priority since he is mostly used in all metas given his godly pull skill. Annie is also a good choice after for her heal buff.
For Ally priority, Andrea as a main dps for ally can be consider topmost. Due to updates for sophia that she can choose her target to follow, she can be consider too. Glenn as a best support is another good choice. Shane will be good but its not that effective to invest in tank characters usually
In short,
1)Abrahim
2)Andrea
3) Annie / Sophia / Glenn
4) Shane / Sebastian / R