There's no need to have all those reserves. In fact, you really can't have all those reserves or else you'll leave your opponent with hardly any horses to pick.

It's really not that hard. Firstly, you pick 1 horse in the feature race of the day, and you pick 1 reserve selection in that race. THEN, you pick 4 other selections, and you pick 2 reserve selections in case of scratchings. That doesn't mean 2 horses in each of those 4 races. It means just 2 other horses running anywhere that day that you'd like to tip if any of your top 4 picks are scratched.