Hi Paul, what are you looking to brew? I assume you're looking for a small kit to get you started.
Most beer brewing kit tends to be sold for doing 5 gallon batches, though I believe there are 2.5 gallon kits on the shelves of some stores.
5 gallons seems like a lot of beer, but by the time you've tasted a few samples and let it condition, offered a couple of bottles to friends and family, it soon disappears.
1 gallon batches are ok for experimental purposes if you're doing extract or all grain, but it's just as much effort to make 1 gallon as it is to make 5 gallons.
Having said all this, to answery question, it is fine to ferment 1 gal in a 2 gal fermenter (FV), as the co2 created will displace any oxygen in the vessel. I have brewed a 3 gallon batch in a 5 gallon FV just fine.
If you want to start with brewing off the shelf kits (cans or sachets of liquid malt extract and a sachet of yeast) I've only seen 5 gal for sale, but I think some shops do 2.5 gal.
5 gallon is the way to go!
You'll need:
- Fermenting vessel/bin/bucket
- Airlock
- Brewing Hydrometer
- Brewing Thermometer
- Long handled spoon or paddle (plastic or stainless steel)
- A length of tube to Syphon with a sediment trap
- Some bottles or a pressure barrel to store beer in. Start with bottles, which can be glass or brown plastic.
- Bottle capper if you have glass bottles
- Bottle caps
I've probably missed something here, no doubt others will remind me.
Why not buy Greg Hughes "Home Brew Beer" book too. It's a good all round book to start with and has lots of tried and tested recipes.