Arrows.
Okay, besides the obvious... Basic equipment. First and foremost, a bow stringer. Much better way to string a bow and a lot safer for you and the bow. Bow square. Gove or tab. Arm guard. Quiver. Spare bowstring, or two.
You'll probably want to get a fletching jig for your arrows. It's hard to find arrows with feather fletchings at local shops any more. Since you can't shoot plastic vanes off the shelf, at least not accurately, you'll need to be able to replace vanes with feathers. You'll probably wind up like most all the rest of us and do nearly all your shopping for traditional supplies on-line.
Assorted things I like to keep with me when I'm shooting or hunting. Dental floss. If I break a serving or my knocking point, I can use the dental floss for an emergency fix. Super Glue gel, to stick a feather back down if it comes loose. One of those spare bowstrings. Butane lighter. I've always got at least one knife with me at all times, but I've come to realize that not everyone is a knife freak.[:-] So, include a pocket knife in this list or, even better, a multitool.
As you go along, you'll figure out what kind of stuff works best for you. So I'm just giving you a starting point.