You could get a decent old Wingmaster for maybe $300 and shoot trap. It’s a place to start without a lot of cash up front. Starting out, you don’t know if you want a BT99, a Citori, or whatever else. When you shoot, you can talk to the other guys on the line. Some will let you try their guns. One guy at our club shoots an old Wingmaster he bought new in about 1960. He shoots in the mid 90% range. If you don’t like trap, or if you like a different gun, you can sell your 870 for about what you paid for it.