30% is what I can afford to lose, but had the roll been repetitive, I would just split BTC0.25 into 5 places and play it 5 times.
VERY bad idea. If you have a mathematical edge over casino, for the repetitive bets, the best tactic is to play with minimum bet increments to reduce the risk of going bust in case of a long losing streak.
Statistically, you'd only win one in six rolls, so losing streak of 5, or even 10 or 15 is very likely to happen. If I recall correctly the longest losing streak recorded on JustDice was over 30 with the odds of 50%.
Splitting the bet into smaller bets to chase a win isn't a bad idea, but isn't the worst way to bet, while more bets then there is a bigger chance to win but we get less profit.
To know how we would roll the bet, we have to set one goal, if the goal is to win big then we need to make some 'Yolo' bets like
1Btcx6(16.5%chance to win)=6Btc
6*6=36Btc
36*6=216Btc.
And this would be the right way to hit the moon, but we need a lot of luck to get that 3 bets streak with those low odds.