Clay shooting can be done fairly cheap.  For most types you want to have a semi auto or over and under gun for the doubles.  For most trap you only shoot singles so an old pump will work fine.  It can also be expensive, if you go to the range you can usually find a couple of the big shooters with as much in their guns as some spend on a car. 

Did they have a skeet range or were you shooting birds thrown out into a field at your buddies house.  If it was birds thrown into a field it was probably more like trap.  2/3 is a good start with trap and would be an excellant start for skeet.  Most Marines have a hard time starting to shoot a shotgun because of marksmanship things they are used to with a rifle like focus on the front site and not the target.  With the shotgun it's focus point is the target and the gun will follow.  It can get quite addicting.  Before I left Pendleton I was shooting with a friend every week and we normally shot 4 rounds (100 targets) every time we went.

Semper Fi

Gunner