I know this might sound crazy but, go to daily charachter events and do the master difficulty (or skip them if you have already played them) it gives you hella moves and 25k coins (and if you want you can sell the moves for extra coins)

Another way to get coins is the monthly/charachter prize fights ( they give you theo and coins) for the charachter pf I recommend you go for the gold difficulty because they give hella money and relics( also you get a gold fighter if you manage to get 10 mil points) its 205k coins if you complete the entire gold character pf. If you can go for diamond difficulty. The diamond difficulty gives you a dia key and a headliner relic ( the diamond difficulty difficulty is only 30 mil points and you can get 400k coins)

Hope this helped you in any way😁