For pursuing wagering contests i suggest to you just stick to the normal bets such as 2x payout and do not use martingale strategy because it will dried your balance rapidly and the worst thing if you use that method for the contests is you will run out your money but at the end of contests you cannot reach good position to get prizes
Agree,,, but this depends on your balance. To build a wager for first few levels, I would say at least 0,05 BTC is necessary to last 1 million bets at x2 payout on starting bet 1 satoshi, but if you have much much less, I would even go for just small bets like 100 satoshi at max chance, and then no increase on loss.
OR my personal favorite is to x2 martingale till maybe 1000 profit, then use 100 on max chance until bust. Repeat again and again.