Guys, everyone enjoys different things in the game, some people enjoy playing the low grade trainer (I have a couple of games where I play that way and I enjoy them) and some enjoy winning every group one in the game (I have one game where that is my sole aim) and there's every variation in between. Obviously Woodie is looking for some way to improve his stock. Also, if he's looking to successfully enter the league at some point, playing the game as is is not recommended. It will take far too long to improve your breeding lines and you'll miss out on many great horses early on.
Woodie- the best way to attain big success quickly is to use artmoney (I'm aware this is 'cheating') to boost your bank account and buy the best possible horses you can. Then breed from them, also using the best game horses that are made available every season in breeding barn. This is the quick way.
Another way, if you don't want to use art money, is to buy horses that are cheap, that are being run over a distance that is not their preferred one. Buy them and enter them in their pref distance in a selling race. Hopefully they'll win and sell for several grand more than you originally bought them for in the after race sales.
There is also a betting way which involves ctrl-alt-del out of the game after noting down which horses win and then opening the game back up and betting on them, but this is really just a form of cheating that takes longer than art money and is more risky. Not really recommended.
Then, of course, if you don't want to use any of these methods, just play until you find something brilliant and then breed from it. Simple, but can take a fair while.
Hope this helps in some way.
-Edit: Also Woodie, it sounds like your breeding lines (if you have them established) are early bloomers. Perhaps try using some outside blood that is confirmed to win at four+. One other thing is, are you running your two and three year olds excessively? It is known that if you run them more than they are capable of handling early on they will never reach their full potential. Make a habit of checking the training section and making sure your head lad is not telling you they're close to being overraced. (Sorry if none of this applies to your situation

)