This group is pretty interesting because there are a few match-ups which could be interesting, namely Orga vs Dimaria for one could be a critical part to the match depending on whether Orga can get some or a lot of damage off on Dimaria thanks to slayer advantage. While Orga would eventually lose out, he could also prove to have an advantage over God Serena if he had Lightning Dragon Slaying magic due to being able to eat it. There are some other interesting things to consider, like Makarov maybe pulling out Fairy Law etc., but anyway, this is how I see it ending up:
First mage through would be God Serena. From what we've seen of the Spriggans so far, I'd say he's the strongest going off what he's shown with his feats, and with a variety of elemental Dragon Slayer magic at his disposal, he should be able to have an upper hand against most of the mages here.
Second mage I'd put through here would be Erza Scarlet. Erza's got a variety of armour to turn to to give her different advantages in the battle, and with the Nakagami Armour she'd be able to tear through a few people, so she would have to go in imo.
Third mage I'd send through would be Gajeel Redfox. The big thing going for Gajeel is his Iron-Shadow Dragon Mode, which would allow him to avoid being hit by most attacks as well as deal out some major damage.
Last mage I'd send through would be Dimaria Yesta. Given Dimaria has her God Soul Takeover, I'd say thats got enough power in it to put her through to the next round. Without relying on that, Dimaria is a decent swordswoman, but really its only the Chronos takeover that sees her through imo.
As for the rest, I'd put Minerva and Bluenote around about 5th, and then we have Makarov in 7th and Orga in 8th.