I started shooting skeet and trap back when I was 11 with my father. He started me right out with a 12ga, but it's really not necessary. A 20ga is more than enough. I remember going to school on monday in 6th grade with a HUGE bruise on my shoulder from shooting a few hundred rounds the day before on the skeet range. I would have really appreciated the 20ga back then!
My first gun was a Remington 1100 skeet, but I found quickly that I preferred pumps. So, my father got me a Winchester Ranger with the interchangable chokes and 28" barrel to make sure I liked the pump. Then I moved on to the Remington 870 Special Purpose (same thing as the Express, but first year they came out with the matte finish and oiled stocks). I shot that for years and it served me well until I fell in love with the Winchester 1897's and Ithaca M37's. The action of the Ithaca is just so smooth that it's what I prefer now.
I agree about Brownings. I'd love to pick up a nice O/U sometime, but they are just way out of my price range. When I can shoot clays just as well with my $120 16ga Ithaca M37 as I can with a $1500 O/U, I'll stick with the cheap, used pump guns.
I HIGHLY recommend looking for a used gun. You can save yourself hundreds off the reasonable price of a new gun and have even more left over to spend on shells and clays.