I still use my aluminum kettle, though it now has just about every add on installed like a ball valve, thermometer and sight glass combo. Aluminum is the lowest cost kettle for starting out, but remember, a kettle is something you will probably brew with for a long time until you eventually go all grain and increase your kettle volume
. I began with a 7 gallon pot, which was horrible for boiling 5 gallons, hot break became a permanent part of my stove top! Going with 10 gallons has always left me plenty of room to brew!