At $10 per bet and 50% POT you are going to need 40 bets a week or 1 race in every 8 to win $200 per week. You sound like you want to have this as income. You should at least leave $50 per week to build up your bank. Have you got enough systems to give you 40 bets per week? Do your systems give you 50% POT? At $15 per you need 27 bets per week and $20 you need 20 bets. So you have to grow your bank to make it easier. The bigger the POT the larger the runs of outs which means greater the draw down.

You have to give a bit more info.