If you're just starting out, the SCSSA match (500 yards) is a good one. The folks there are super and while it's not as formal as other F Class matches, even though you don't have pit service it's still highly value adding. As long as you are not hung up on racking up a high score per se, and more interested in developing your basic long range prone technique in order to shoot tight groups at distance, then it's a great place to gain experience. If you have a good spotting scope and can actually see your bullet holes @ 500 then it's a bonus. I shot there recently and while my score wasn't great on the first relay, I was pleased none the less because I had a nice tight 6" group (20 shots)... only it was low and to the left (lots of 7s and 8s)!
Once I adjusted my zero for the next relay, my score went up considerably. All in all I was a happy camper!