Work on your own actresses, so that you don't rely on casting.
Getting a good girl with casting is very hard (it did happen for me a few times, though, but I admit it was rare). I think I spent more than a million in total on casting, and only got two or three 100-sex-appeal girls. This is just a matter of luck, so you need to give it every opportunity you can.
For me, having the best and fully developed car for city cruising worked best as the girls source, with going to parties being a close second. Right now, all my whores and actresses have sex appeal of 100, most of my football girls do too (not that it matters much), plus I have about a hundred divine girls lined up for pick-up. So, you don't really need casting.
