fair enough.
I'm not a big fan of systems because they are too rigid, but I do use a set of guidelines to try and reduce the no of losing bets. Within those guidelines i do my own ratings and bet the overs.

Regardless of what method you use the profits are made by backing the horses at overs and letting the other selections pass by.

I prefer to make only 5-10 bets per week, because I don't like betting on races which I don't have a good understanding of?

Question for bECAREFUL?
If you're betting on 50 races per week, how could you possibly know the horses well enough to accurately frame a market and bet the "overs"? They would require 50 hours per week commitment!