If you can get the 5 gallon carboys at a local pool supply, that's great. Otherwise, it's really no big deal at all to use 1-gallon jugs.

I have an 18x36 inground, and I use about 1 gallon per week. I also keep a single tablet of tri-chlor floating in the pool at all times, just in case I forget to check the pool for a day or two, I never have to worry about it being completely without chlorine.

I pick up a jug or two of bleach every week when we go to Wal-Mart. Very cheap and easy way to chlorinate the pool.