If you are planning on 4-5 chicks a shoe box with some bedding in it should be adequate for the ride home unless it is very far. If you have a long drive bring something that will hold water and bit of chick starter. Most important thing is to have brooder ready to go for when you get home. Also, look them over well before purchase for bugs, foot problems, etc...
As for money....that depends on what you are wanting to purchase and what you are able to spend. If you are looking for chicks from show quality birds or rare breeds you will pay more, but if you are looking for "barn yard mix" a few dollars a chick is typical for this region.
It also wouldn't hurt to get some photos or a book to take with you for helping with selection. If you are looking for buff orpington's specifically it might to be nice to have a pic of a male and a female so you can have more guidance on selecting.