Save your seat money and buy some the Cruiser model from Moto-Skiveez's.
I ain't saying this myself, but a good friend bought these things and he claims the edges of the cushioning material cut into his leg. Apparently it was very uncomfortable.
I use those elastic bicyclist shorts for undies and they work pretty well as far as not getting stuck on your arses.
You can get cheaper versions of these at most department stores: JC Pennys, Sears, Macy