Sometimes I up the bet if I'm losing. I'm like you a low roller, - .09 - .90, but recently upped it to .18 - .90
I up the bet when I feel I made enough spins on the low bets but haven't hit any free spins yet. It's that feeling of I know it's gonna hit. Obviously I'm wrong more than right.
But I know when I up a bet, I spin it for at least 15 - 20 spins in the high bet before moving back down.
Or you can just follow a system of 10x - .18, move to 10x - .45, back down to 10x - .27. But you need to continually follow this system regardless of the amount you get. Needless to say this makes slots boring. But it seems to work.