You can pick winners and still go broke. On prediction markets, how much you stake matters as much as what you back — bad sizing is what turns a normal losing streak into a blow-up. Bankroll management is the boring discipline that keeps you in the game.
Flat staking: the safe default
The simplest plan is to risk the same small fraction of your bankroll — say 1-2% — on every bet, regardless of confidence. It won't maximise growth, but it's robust and nearly impossible to blow up with. If you do nothing else, do this.
Kelly: sizing to the edge
The Kelly criterion sizes each bet in proportion to its edge and the odds — bigger edge, bigger stake. It's growth-optimal in theory, but full Kelly is brutally volatile and unforgiving of overestimated edges. Almost everyone serious uses a fraction of it (a quarter, say) to cut the swings.
Caps, because your edge is an estimate
Every probability you use is an estimate, and estimates are sometimes wrong. Hard caps — a maximum per bet and a maximum total exposure — protect you from a single mispriced 'edge' doing real damage. Momus sizes with fractional Kelly and enforces both caps on every position.
For the theory behind the sizing, read the Kelly criterion, explained.