If you don't have a smaller fermenter, I would buy a 3 gallon PET Carboy. You can get them from Lowes or Home Depo for $5-6 each with excellent brewing water. Look for a triangle on the bottom with a "1" in the center. This is PET. If you do this it has to be PET. I use carboy caps with these.
Use this as your primary, buy two if you want to do a secondary.
If you have hopped mixes & unhopped mixed brew 2.13 gallon batches.
The instructions for a their beer making is a no boil process. Like Coopers or Barons. Boiling only muddies the hopped flavor.
MRB Extracts Only - Boil 4 cups water. Flame-out. Add the hopped can w/ the booster - (corn sugar & malto-dextrine) or one can each; hopped and unhopped. Steep your aroma hops; 1/4 to 1/2 oz per two gallons. Hops w/ 4-8 AAU's or think of your IBU's... Dump in fermenter add water to 2.13 gallons. Pitch.....
If you use DME use 1 lb and about 2 oz crystal malt. Steep crystal for 30 min < 160F with 1 gallon water. Boil, bitter and flavor hop as normal. Flame-out. Pour in one unhopped extract. Stir till mixed. Steep Aroma hops. Add to more water to make up 2.13 gallons and so on......
You can down load their PDF instructions at;
http://www.mrbeer.com - Go to the download section.
The no boil seems unnatural but works.
They also have 100's recipes, you can improvise off of them. You can make a decent beer that won't disapoint you. You may be surprised.
As you can tell I got these as a gift too. Getting a fruit cake or being regifted is much worse.
If you make seasonal beers, the smaller batch is nice. You will like not having pumpkin ale in February!!!