Sheet pans

My sheet pan is one of the most-used items in my kitchen. I love it. I highly recommend purchasing your own high-quality, heavy, aluminum, rimmed baking sheet. You can use it for practically everything that goes in the oven-cookies, vegetables, meats, galettes, breads, biscuits, etc. These pans (called half sheets, as they're half-sized compared to a full-sized commercial pan) bake/roast evenly, don't warp, and they're the perfect size for standard ovens. What's your new pan going to cost, you ask? King Arthur Flour sells one for $17.95 or 2/$30, Williams-Sonoma for $17.00 or 2/$30, but mine? I got it for $5.00 at a commercial baking supply store in Chicago. That was several years ago, but they haven't raised their prices too much. Now they're $6.50. That was worth checking around for!
Of course, along with your pan, you should get some parchment and/or a silicone baking mat. Parchment is wonderful. You can slide the entire sheet off your pan or lift your baked goods right off and reuse it until it's practically no more. Then you don't even have to clean your pan. Parchment comes in rolls or sheets from the same sources mentioned above (and can be used for a wide variety of things in addition to lining a sheet pan). Again, with a little research, you may be able to find this cheaper. I got a large stack of sheets from a caterer at little cost.
The silicone mats fit perfectly into one of these pans, are nonstick, and are super easy to clean. Haven't ever found a great deal on these, though.
For some professional opinions on baking sheets and liners see this article from Fine Cooking.
Now I have my eye on a quarter sheet pan for smaller recipes and for use in the freezer.

P.S. My sister crocheted the lovely hotpads in the photo above and I can't bring myself to actually use them for fear of ruining them!