What is the best way to use prep races? Using them alot? Only a little? Right now I'm using them pretty much only for the Triple Crown races and the Breeders Cup races.

It really depends on the races you're prepping for - I think the maximum number of preps you can have for a single race is 10. Also, season-long preps work much better in SO5 than they did in previous versions, which helps when it comes to the big races at the end of the season. For the default schedule, I used preps very sparingly, as I didn't want to over-complicate things, but with my own schedule that I'm creating I plan to make far more use of them, as they're a very useful tool when it comes to assisting the AI in the game to make things more realistic, especially when you're creating a worldwide schedule.

One tip I would give is that if you're heavily prepping a big race, and there is another big race less than two weeks before the target race that might also be attracting similar horses, you might find that the unprepped race suffers from a depleted field, as horses might be more likely to bypass the race in favour of the heavily-prepped race less than two weeks later. It's just a case of trial and error sometimes to get the balance right, but it can definitely pay off when you get it just right

would this not make it even more realistic? for example you would have a weaker field for the german derby than in say the irish derby or grand prix de paris which are on at roughly the same time of the year, this happens in real life so i think it would add an extra layer of realism to the game, if thats even possible

Just wondering, what is the purpose of prep races in the game and what do they actually do?