All 3 of the wind characters u mentioned are pretty good. Gaia I already have and she's pretty good defensively and taking hits. I have yet to awaken her as wind isnt my core team. Also I hear that Azazel is a staple for wind teams too and also gets better once awakened too.

Honestly it comes down to what character appeals to you and how much they benefit the teams you choose.

I have amon unleashed and can say shes great for taking down the rage meter of a boss on dark teams, however dark teams are extremely limited in terms of Healers in keeping the team alive, as it only has of 1 SSR in the dark element that can heal that is Osiris. There are SR healers but again Dark team for me personally is pretty lacking.

Having a choice is hard but I'd stick with your core team.