If I were you, and I wasn't going to spring for a bar tender, I would probably just do 2 or three mixed drinks.
Hunch punch is the cheapest to make in big batches, and can really help you stretch a budget.
Out of the mixed drinks you listed, the most popular are going to be the punch, the margarita, and the cola and alc.
The OJ for screw drivers is expensive, and girls love screw drivers so you'd be smart to get a lot of OJ if you are going to do those.
Not as many people are fans of Gin and tonics, and the ingredients can get pricey.
And I would skip the price of vermouth as well.
Its usually cheaper to by a bunch of a few things than to buy a bunch of different things.
I would also get PBR, Keystone, Natty Light or some other cheap equivalent for your beer.
Wine's going to be expensive, I would try to have a few bottles but don't buy a ton. Try and get people drinking the punch.