There are a few different approaches if you want to use mathematical strategies. I find the Kelly Method to be the most popular and the most comprehensive.

Kelly Method:

This uses two key factors; (W) winning probability and (R) win/loss ratio. The result will tell what percentage of the money you should apply when placing your bets (Kelly%). This formula is used to determine the optimal size of the bet when the expected profit is known.

​Kelly %=W - (1 - W)/R

Kelly %=​ Percent of money to put into a single bet

W=Historical win percentage of trading system

R=Trader’s historical win/loss ratio​

Hope this helps you out. Best of luck!