Ally/Neutral Benefit Most Priority!
1. Abraham - One of the top choice that you should focus on. He's the meta now, he's everything that you need and most of all he's the most overpowered unit that you could'nt imagine. He literally can tank, your main damage dealer and ofcourse a good crowd control unit. Never sleep on him because he will carry you in different stages, camp defense, supply runs, joint combats, etc.
2. Glenn - Let's appreciate first that even he's a support unit but he can actually be a substitute tank for you. Okay now here's the deal why you should second prioritize him, its because in total war and joint combat he really excels well. He barely distributes a decent buff to boost the attacks of his companions and also can heal those who takes damage in every run. Not gonna lie but he really helps me to deal more damage especially if Ezekiel and Shiva is present they're the real monsters to support your damage dealers in its best.
3. Sophia - Now that our baby gurl can be designated on which she will go on first to support it, no doubt that she's the 3rd option for you. I know its another support but the fact that she can reset the ult that she follows no doubt that its one of the biggest game changer unit for you especially in total war and joint combats. A combo of Ezekiel and Shiva, Glenn and ofcourse to our baby gurl they're the most lethal combos that you could have.
4. Kate - Your second best option of damage dealer. We all know her potential is pretty good no matter what battle you put her. I just put her in the 4th place in your prioritize because she can manage herself no matter what the situation is.
5. Magna - My last priority you need to invest. They're making fun of her because she's a niche that the only thing that she could do is buff all unit with her speed and after she's useless but for me its a no, she excels well also as a damage dealer with her healing abilities for her to survive in a long run. Having her is much more important that you could imagine. She barely manage to survive and deal damage to those annoying back row enemy units. So better not sleep with her and make sure her to be your option.