Learn as much as you can about money management first. Make this your first priority. This means knowing what to look for whilst you test a particular strategy, like the Longest Losing Streak, Largest Losing Trade, Win/Lose Ratio, and Drawdown. A 90% win rate may at first look promising, but if your strategy wins $5 per winning trade, and loses $50 per losing trade, your account is going backwards. Likewise, if you have $10,000 in your account, and a Longest Losing Streak of, say, 3 losing trades in a row with an average losing trade of $4,000 in value, it's obvious that you risk blowing your account if 3 losing trades should happen to come along. The risk increases if each of these 3 losing trades happen to be the size of a Largest Losing Trade.
Most traders seem to get this money management thing back to front by first determining a set of money management parameters, and then applying their trading strategy according to those parameters. The problem with this approach is that you don't know if these parameters are suitable for the strategy you are using. You can only obtain meaningful money management data by first testing your strategy, and secondly analysing performance results. For example, simply by reducing a $50 loss to a $40 loss, as in my first example above, the strategy becomes profitable, and reducing the average losing trade from $4,000 to $3,000 as per my second example, this strategy also becomes profitable and safer. You cannot make these adjustments without access to performance data.
Test a strategy first. Gather performance data. Make necessary adjustments. Test again. Repeat...even when you have a successful trading strategy and are now trading live...repeat!