I usually play 20-50 dollars, with an odd $100 if I have had a nice cashout to my e-wallet, and there is a very attractive match bonus.
I'm taking a kicking with the exchange, so I make a lot of $30 deposits...that's nearly $50 Cdn, but $50 for the casinos that take CDN funds.
It's sometimes hard to tell how much is left on my prepaid, with the exchange rate differing from place to place, and the rate it is settled at is different from what is deducted immediately "on hold".
3Dice pretty much gets my "hmmm...wonder what is left on my card" business, because I don't think they will bust me as a fraudster if a $30 deposit is rejected, and I try $25 next.