I like to do a double on the Kentucky Oaks (three year-old fillies that run at Churchill Downs the day before the Kentucky Derby) and the Derby itself because it can pay well if you don't pick only the favorites.
The other thing about betting fillies is that, well, they're crazy. Any darn thing can happen.
In the Oaks, I think the favorite's probably going to be the Pletcher horse, Rags to Riches. With Garrett Gomez aboard, if she gets a good trip, she should totally win. So you have to include her on your ticket. Others who might come in at a better price are High Heels, and maybe Dreaming of Anna is worth a look. The word is she had a problem with a growth spurt in her back legs and consequently didn't do well in her last couple of races. But the problem has been handled now, so "they" say. She did spank last year in the Breeder's Cup Juvenile Fillies, but then again she had post position one and there was a decided track bias that day for the rail. Then again, that she's fit seems pretty clear because she just had a 5-furlong bullet at Churchill Downs of .58, which is fast.
Other fillies that might show up are Cash Included, Octave, and Mistical Plan, but ya just can't bet em all.
I still need to 'cap the Kentucky Derby, esp. now that I hear there's a 50% chance of rain that day ... some horses just can't handle slop, so that might give me some more ideas about which ones to at least toss out.