How you bet doesn't matter. If you want to give up the lowest edge while having a chance to win something decent, do small bets with small odds to win.
Lots of small bets will have less variance and the result will trend towards the house edge the longer you continue. A smaller number of large bets will have more variance so you have an opportunity to have good luck and come out winning.
I confirm. To put that with figures, you have 0.5 btc balance. A single bet with 0.5 and you have 47,5% chance to earn 0.5 more, but 52,5% to lose all your balance.
With ten bets of 0.05 you have 0.475^10 = 0.05% chance to earn 0.5 more (ten wins), 1% chance to lose all your balance.
With one hundred bets of 0.005 you have hardly any chance to earn 0.5 more (4,5e-31% to be precise).
The smaller your bets are (and the more you bet), the sharper is the result distribution (thus less variance), distribution which is by any means biaised towards negative gains by the house edge (you have more risk to lose all than chances to win all).