For the Gwent card game in Witcher 3, I notice that I can wager a bet when playing, such as betting 5 coins in the hopes of winning back 10 coins, therefore doubling my investment. I assume that there are other points where I can wager more than 10 coins, which is the most I've seen so far.
What's the most that I can wager in a single game, and where are the games played? Is it actually a reasonable way to make money, or are there faster ways?