[Lynn Eades]

The air consumption depends on the type of gun and the jet in it.
Compressors are rated by the FAD (free air delivery) in cu. feet per minute.
It's hard to get apples for apples, but go for the biggest one you can afford.
A large receiver (tank) will let you blast longer before the pressure drops off, but it also means that you have to wait longer to pump up again, if the pump is to small.
Keeping the media (sand) dry is very important to having it flow freely, and work well.
LASTLY, but MOST IMPORTANT. A young fella like you needs to be very careful when it comes to dust, and when blasting it is hard to avoid breathing at least some of it, sometimes. Because of this I would seriously reccommend using a media that is NOT silica based. Silicosis leads to lung cancer. Buy some garnet or other suitable media, and a respirator. They're cheap compared to maybe cutting 20 years off your life.