congrats on getting your first meta ^^ I would definitely try and max breakthrough kurenai if you haven't done so and aim to get asuma windblade from ninja collection. That'll not only buff edo minato it'll sustain him. In terms of seeking out a new ninja a 5 kage madara is ideal :)

Madara 5 kage, Minato EDO, Wind main, and Gakido Full ST. You can basically use mystery from round 1 to 4 while denying your opponents mystery.

For now go with this:

X x x

Wind main edo minato x

Sakura summer Guy x

Talents: 32111 or 32131, summon: any 10 combo chase one you own (best koh).

For the future, try to get gakido breakthroughs (full free) and a barrier ninia for him (both a booster and a breaker are fine. The current best option is gaara kk)

If you mean the summon mystery, the specific stones are usually in treasure of the sage event, they cost around 250-300 coupons per fragment when appear and you need 15 of them to bring it to level 3.