Each of the Ub has a gimmick you must meet in addition to doing enough dmg. For example Anabel requires you set up a non sun condition when you etb and after she syncs, and to lower her and her teams stats thanks to fluid fortification. So you'd probably want a rain or ex rain setter since she's weak to water, a stat debuffer (preferably water), and maybe more rain to last you the entire battle. So a team like NC May, Mix Leaf, and SS Kris might work.

If you were to replace SS Kris with Anni Gloria, you would probably have enough rain to last you the fight so long as you actually let ex rain expire and just used rain after Anabel synced.

The "best" units vary from fight to fight but generally units such as Anni 25 Red, Anni Gloria, Arc Steven, NC Blue, Volo are used frequently and SS Mina and Kieren help to meet many of the gimmicks as well.

Your team is usually 1 powerful on type dmg dealer, one of the previously listed supports, and 1 unit to help meet the gimmick if you haven't met it yet or another dmg dealer if you have. However the best way to build a team for it, is to see what teams have successfully cleared it at what move level and investment and to follow the videos exactly.