If you are headed out the door with the intention of getting laid, think bigger Than just condoms in the purse. Here is a guide for packing the survival kit of modern casual sex. You'll want to find a small attractive bag that zips closed so your goodies don't fall all over the place. Duh, this is pretty obvious. But remember to bring a variety.
Many people are allergic to spermicide.
Use spermicidal condoms, preferably non-oxynonal 9, if you can. But remember also to have non-spermicidal so you can cover all your bases. Though you ought to ditch them if you find them, there are guys out there who will whine about wearing condoms. Wear your own. Female condoms are very different from the male versions, so if you don't like one, it doesn't mean you won't like the other.