1. A few photography books checked out from your local public library, assuming you choose books appropriate to your needs and truly study them, will cost nothing and should improve your images more than yet another accessory.
2. Visiting the art museum will likely cost little or nothing, and again - it'll improve your work more than would another accessory.
3. Feedback matters. We improve through feedback. Join a local camera club, and let your work be ruthlessly critiqued. Enter your club's competitions. Learn how to politely and constructively critique other members' work.
4. Most community colleges offer inexpensive classes on various aspects of photography. I'm taking a Photoshop course at the local college, this fall. (For some reason, no "Photoshop CS for Digital Photographers" courses were offered at my high school in 1979. So I took Advanced B&W Darkroom, instead.)
5. Don't be too much of an equipment snob. There's a saying sometimes heard in firearms conversations, "Beware the man who owns just one gun; he probably knows how to use it." Similarly, that guy standing next to you, taking pictures with the 30 year old 35mm SLR w/50mm f/2 lens, may just know how to use his equipment to its best advantage. And, consequently, shoot rings around 98% of us.
6. Place little faith in most magazines' published equipment reviews. Our sun will go nova before Pop Photo prints a negative review of a piece of Nikon, Canon, etc., equipment.
7. Unless you've a good and compelling reason to do otherwise, always shoot in highest quality mode. It takes no more than a few seconds to resize a high resolution original, should you need to shrink it down for email or a website. But nothing can add information to a low resolution original.
8. Fine-tuning an image in Photoshop (or Paintshop Pro, or something similar) is not cheating. Sure, it can be overdone, but there's nothing inherently wrong with adjusting contrast, using unsharp mask, or the like. The saying used to be that great photos are made or lost in the darkroom. Well, the computer is the digital photographer's darkroom.
9. If you delay buying until the new and improved model is introduced, you'll wind up never buying. Because there's always a newer and more improved model rumored to be introduced at the next big trade show.
10. If friends ask you to shoot their wedding, because they know you're not a professional or anything but they're on a really tight budget... run away. Okay, if that's not practical, consider hiring an inexpensive professional photographer as your wedding gift to the couple. If that's not practical, consider buying a bunch of disposable cameras, putting a few at eah table, and inviting guests to snap pictures, then deposit the cameras in a big "Wedding Pictures" bag on the way out. If that's not practical, run away. (Amateurs should be extremely reluctant to photograph weddings, in much the same way that 1st year medical students should be extremely reluctant to perform heart transplants.)
11. If you don't derive a significant percentage of your income from photography, you are an amateur photographer. Having once sold a picture to your hometown newspaper doesn't make you a professional. It doesn't make you a semi-pro or a prosumer (avoid both of these terms). What it makes you is an amateur photographer who once sold a picture to your hometown newspaper. And there's nothing wrong with admitting that you're an amateur.
12. You're probably less of an expert than you think you are.
13. Try to spend more time taking pictures, than you spend on the Internet writing about taking pictures.
14. If you just feel burned out, and don't want to pick up a camera again, take some time off. Put the camera in the closet, and forget about it for a while. Days, weeks, maybe months. Eventually, you'll probably start feeling motivated to take up the camera again. And when you do, you may find your work has improved over what you were turning out before your break.
15. It's a tool. Treat it with the respect and care a precision tool deserves. It's not a fragile relic, too delicate to be used. Yes, it's sort of expensive. Well, so is a car, but if I told you I don't take my car out in the rain, or drive near sand, for fear that it might result in my car no longer remaining in pristine, mint new condition, you'd be right to think I was crazy. Camera equipment is only worth having if you make use of it! (No nitpickers bring up the possibility that it's a $1.2 million classic, one-of-a-kind car, or a digital camera handmade out of the finest, most delicate porcelain.)
16. Always stop at #15.