Ah, the final battle royale. Here's my thought process for who I've voted.
The first person I'd put through would have to be Natsu Dragneel, its a no-brainer really. He's one of, if not, the strongest person in the group magic-power wise, and his Dragon Slayer techniques are very strong and ranged, giving him spells to use in CQC as well as large AoE spells as well. Given Natsu is also one of the strongest characters in terms of hand to hand combat expertise as well as the enhanced strength, senses, endurance, durability and speed that he gets from being a Dragon Slayer, as well as his modes like Lightning-Flame Dragon Mode, Flame Dragon King Mode and Dragon Force, he's unstoppable to pretty much everyone in the group.
The second person I'd put through would be Wahl Icht. With the ability to use different weapons and enhance different attributes of himself (eg. Assualt Wahl to increase his attack power) Wahl is a very dangerous opponent. He's shown he's also got Etherion up his sleeve to use that in the battle as well, so that makes him an even bigger threat.
The third person I'd put through would be (Third Origin) Sherria Blendy. Needless to say, Third Origin is an incredible power-up that gives the mage all of the power they'd achieve in their lifetime, and that definitely puts Sherria right up there in the group. With Sky God Slaying Magic, she could not only do some real damage to her opponents but she can also heal herself which gives her an ace to fall back on when the battle really heats up.
The fourth person I'd put through would be Gray Fullbuster. While Gray isn't the strongest when it comes to magic power, what he lacks there he more than makes up for with his imagination for his Ice Make Creations. Throw in Ice Devil Slaying magic and Gray becomes more of a threat, with more techniques to throw at the others in the group. Gray barely makes in, only getting in with hype tbh, but I'm willing to give him that.
As for the rest, here's how I'd rate them:
5. Neinhart
6. Kyouka and Rogue
8. Marin