I am asked a lot on whether to buy new vs used equipment. My thoughts are that kids under 12 don't wear out equipment the way an adult might. Kids tend to just outgrow the equipment--so buying second hand doesn't mean you are purchasing equipment that is past it's prime--more often than not, it was just worn for one season and then outgrown.
The only item I would buy brand new--and I would spend a few extra dollars on, too--is the helmet. Your son or daughter's safety is the most important thing and a proper fitting helmet is critical.
Source: Randy Martin has over 15 years coaching experience and is building a unique program to help both players and parents.