Many people feel that to improve their photography, they need to invest in expensive equipment. In fact, when a person sees a beautiful image, one of the first questions asked is: "What kind of camera do you have?". But does it really matter? Do we concern ourselves with what kind of brushes Rembrandt used? What is the brand of piano used by Beethoven? When we see a beautiful piece of furniture or a well built home we generally don't think about the tools used to arrive at the finished product. We appreciate the result and the talent and skill used to achieve it.
A camera is a tool and the one using the tool needs to have a degree of ability. That's why I would probably not hire a monkey to build my house even if he did have the latest and most expensive air nailer.
That is not to say, however, that equipment has no impact on the quality of our work. More expensive cameras generally have larger sensors and can produce better image quality, especially on larger prints.Cameras with many settings and more manual controls will give you more options and flexibility. Specialized zoom and telephoto lenses can greatly improve the images captured by a wildlife photographer. But I have seen frame worthy images made with a 99 dollar point and shoot, a cheap tool. So really, to me, the most important tool in photography is the one behind the camera....( wait, that didn't sound right ).
Spending thousands of dollars on a camera may improve your photography a little because you may feel more motivated to learn and use the camera simply because it cost a lot and we want to justify the expense. On the other hand, for some people, expensive dslr cameras,lenses,filters etc. just are not practical to lug around and it takes time to understand how to use them. This may be discouraging to some and they stop trying to improve their photography.
That is why I believe a persons best investment is to develop their ability to 'see'. Look at your subject with a different eye. Try unique angles, experiment with different viewpoints. Climb a tree, stand on a ladder,lay on the ground. Don't always shoot from head height. Spending time looking for a fresh viewpoint can make even well known locations, original and unique.
The image below illustrates this point. Most people, upon seeing a subject like this would probably stand back and snap a picture of the whole truck, basically documenting what they saw. I wanted to get a fresh view of this truck. I laid on the ground and took pictures of the front, side, rear. I wanted to include the sky. The broken headlight and windshield, for me, were details I wanted to include and couldn't be achieved had I just took a quick shot from the side. So, walk around your subject if possible, use your imagination and take lots of shots. This can be a very economical way to improve the quality of your photography.