Rickyford
You are getting a lot of advice and some recommendations, but no explanations.
If you already know this, just ignore this post.
Skeet and trap are two totally different games, and the fact is that you need two seperate chokes to successfully compete in them.
Skeet will generally require an open choke. Competition skeet guns all have a "skeet" choke and the barrels are generally 24 to 26 inches.
Trap will generally require a tight choke, usually full choke and most barrels will be 28 to 30 inches.
Skeet is a game of close ranges, with birds going away, coming at, and crossing in front of you. A tight choke will be a handicap.
Trap is a game of long shots with birds always going away. An open choke will be a handicap there.
It is possible to use the same gun, and even the same barrel for both games, most beginners generally start out that way. But you will definately need to have screw in or adjustable chokes for that barrel.
I started with a field grade 1100 12 guage.
I shoot a lot of skeet. I used to shoot a lot of trap, but after a while found I didn't like it as much, I find it boring, and eventually quit shooting it pretty much all together.
I have only shot sporting clays once, I liked it, but I don't have the experience to give any advice on it all.
Good luck, and have fun.