Good advice has been offered. I would like to end by stating:
you must first learn (teach yourself) to eliminate horses who have no chance of finishing first or second. This is accomplished through practice on many races. They may be used for a lower layer in an exotic.
If you have a problem narrowing a race to 5 horses , you should pass the race find another.
Lastly, you must become proficient when picking pacelines.
If you are unable to do this, no money management plan will provide you with
the results you seek.
good luck,
BobC