save for fuku and then go for 4* mintao edo

Yeh try to get it during fuko so you get 2 ninjas you want, or at least power + ninja. Kakuzu is boring but still very strong all around gnw/arena/fast in swb.

First of all, congrats on saving up 20k, I know it can seem daunting if it's your first time trying to save. Second...I'd recommend saving a bit more lol. Just to, like, 25k. 30k if you're feeling patient, but if you don't have any good meta ninjas right now, in my opinion it's more important to just save to 25k and get one as soon as you can (when a Fuku deals comes around and you have 25k coupons). Getting your first good pos 1 carry ninja is worth the slight loss in overall value you get if you only spend 25k in the Fuku (vs 30k) deals event because it will make other aspects of the game so much easier and more fulfilling.

In terms of who you should get. It's hard to say. The top tier ninjas right now are 4 stars full breakthrough Edo Minato and Rinnesharingan Sasuke. Breakthrough Kushina and Kakuzu are also very good. Honestly, if this is going to be your first meta carry ninja, I'd go with Edo Minato because I think he's more easy to make teams around with limited support ninjas compared to Rinne Sasuke and Kakuzu. Minato can go in a lot of teams, Rinnesasuke might be slightly better overall but you need very specific support ninjas for him to work as best as he can and those ninjas are also harder ones to get. If you could show us a screenshot of your ninjas maybe it'd be easier to give a recommendation?

Good luck!

I have lvl 57 with weak ninja. The most expensive ninja in my team is Dan xd

In whats events i should spent coupons? If i will get Edo minato which is 2nd ninja to buy for a better Combo?

So, if you're going for Edo Minato, the support ninjas don't matter as much at this stage. You probably won't have enough coupons left over after getting him to immediately get another ninja. If you spend during a Fukurokumaru's (Fuku) Deals event (like the one on currently, but don't spend yet, since you don't have 25k coupons and won't be able to take advantage of the full rewards) you can essentially get 2 ninjas for the price of 1. But, its not a guarantee the ninja given out in the Fuku deals spending rewards will work well with Edo Minato. Either way it's a nice bonus though.

As far as I've heard, going from 0 to 180 (enough for 4 stars) frags of Edo Minato in one go is very expensive, like 30-40k or something. So you might wanna be grabbing the free frags of his you can get in the weekly events with point rewards (not spending coupons) while you keep saving up so you can make it a little cheaper for yourself in terms of coupon cost. However, it's ok if you can't get him from 0 frags to 4 stars in one day through spending. His non breakthrough form isn't the greatest in PVP anymore but it will still serve you well in many aspects of the game and make it a lot easier. But just keep chipping away at his frags and saving to get him 4 stars.

In terms of a secondary ninja to have with him. You can try Edo Itachi. He doesn't have any specific compatability with Minato but he's just a great support ninja all around and can fit on many teams. You could also try Edo Roshi or Seven Swords Killer Bee (don't spend for them, you can get them for free in the time limited jinchuriki seal treasure event using seal scrolls) since they both are good jinchuriki assist ninja. I'm guessing you won't have either of those guys for a while though so a team you could make, with more common ninjas you might have would be like:

Non-BT Edo Minato's biggest problem is his mystery's long cooldown time after use. You can avoid this by using wind main's Dance of Impetus mystery refresh skill - pretty much everyone did this in the days before he got his BT. Dan is a good pos 2 ninja since you have him, he can be used to stop your opponent from setting up stuff in round 1 (opposing barriers, etc.). Gaara will further buff Minato when his barrier is up. Right now, Gaara is probably the easiest ninja to work on. If you don't already have him, start getting his frags from the ninja collection scrolls (not the seal scroll treasure draws, the "collection" tab thing in the "ninja" interface). You can buy like 5 of his frags every day using survival trial points. Get him and then get him 4 stars and his breakthroughs. It's easier than it seems it just takes a while because of the limit on frags you can get every day. But he's a good support for wind ninjas that you can get early game for free.

Good luck with your saving and let me know if you have any more questions.

I did 25k, so the final answer is: Edo minato 4 stars or Sasuke rinn 4 stars?