Fast mages

Damn, thats a tough one. Celica has a really unique tome thats gimmicky, but super strong. A free swift sparrow at 100% (that imo can easily be abused with an ally with renewal + reciprocal aid/ ardent sacrifce) Without her tome's ability she is a worse tharja. Mae isnt that bad either, unfortunately she is indeed outclasses by linde, even with heavy inheritance invests. Alternatively, Nino is considered a pretty great mage and not hard to come by. Imo, if you want to spend orbs I would say roll the female mage banner only if you already didnt have Sanaki, because there is no worse feeling than getting somebody you dont want when gambling. The shadows banner seems like a good roll. Even if you get the healer, her staff ability seems really strong.

I think everyone will get 20 orbs from the event so you can try and use those for mage gauntlet summons. Tharja and Celica are different yet similar. Tharja works best if you have a support unit like Eirkia, Ephraim, Sharena and Celica works better if you have units that can heal her.

Overall the mages in the mage gauntlet summon are superior to the shadows summons. If you want to avoid Sanaki, just roll on blue and green orbs for Linde or Julia, both whom many prefer over Tharja.

Definitely try rolling for Julia. I was able to make a Arena team without blue unit possible mainly because of Julia. She can almost take care of all mage units alone. Linde and Tharja are great too. It best to have atleast one of these glass cannon mages(Tharja, Linde, or Nino).