LP hacking works, so an auto win hack is trivial. Also, I know it works on Casual online, but can't get it to work on ranked.
Gold coins are sadly server sided, but if someone more knowledgeable than me has a crack at it then maybe you can boost duel win payouts.
I couldn't even find the value for gems but I'm sure they're server sided too.
The timer on ranked is server sided. I attempted to freeze it, but it seems that the freeze is only client side.
That's what I've tested so far. Will edit it in more things I've tried as I test them. I'm gonna look into hacking infinite attack on a monster, but I've yet to attempt to figure out how their attack values are stored. I'm thinking it might be by monster slot on the field, but we'll see ^~^