The first thing we spend money on. Contrary to popular belief, a more expensive model will not make us better photographers. They may,however, make certain tasks more convenient or even possible. I believe that all current manufacturers produce good cameras and all are capable of making fine photographs. In the world of DSLRs, Nikon and Canon are by far the most popular manufacturers. I am currently in the process of rebuilding my entire system as I have recently switched to Nikon from the Canon system that I used for 20 years. Below you'll find my choices for Camera Bodies and Lenses.
My camera of choice at the moment is the Nikon D4. The primary reason that I choose this camera is for the extremely high quality image it produces. Along with its weather proofing, durability, and high frame count this camera has excellent noise characteristics at high ISO's and long exposures.
Lenses are one of the most important components of your system. A higher quality lens on a less expensive camera is better than a low quality lens on an expensive camera. There are several things that increase the cost of a lens and not all of them may be important to your type of photography. A fast lens( f2.0 or 2.8) for example, is almost always more expensive than a slower lens (4.0 or 5.6). If you have no need of shooting in low light, perhaps speed is something that you can do without. Some lenses have better coating on the front element which causes a higher quality light transmission. Others are better sealed against rain and weather. Typically, you get what you pay for. If you see two similar lenses with dissimilar prices from the same manufacturer, the more expensive one is likely to be faster, better sealed and or have a better lens coating. The exception to this comes from the non camera lens manufacturers. In general they sell lenses that can produce very high quality images. The difference here is usually in the "fit and finish". They may be as sharp, but in some cases, their auto focus is not as fast, or they may not be sealed as well or a larger percentage of the construction is plastic instead of sturdier metal. However if sharpness is primary concern, many of these lenses are worth a look. dpreview.com will provide you with trustworthy lens reviews.
Cable releases (Remote Switch)
A cable release helps keep the camera vibration free when using a tripod. Although you can use your self timer for the same purpose, it doesn't allow you the same precision timing.
Tripods are an essential tool for many disciplines of photography. They not only hold your camera steady but they also slow you down which helps you focus on your composition. Look for a tripod that fits your needs. Typically heavier tripods (aluminum) will be less expensive. Lighter tripods (Carbon Fiber, Basalt) will be more expensive. If you backpack a lot, you may consider a lighter and smaller tripod. You can then loop your camera bag over the tripod to weigh it down. if you don't spend a lot of time carrying your tripod, slightly heavier models can be less expensive. I have found both Gitzo (the industry standard for professionals), and Manfrotto (the solid workhorse), to be excellent tripods. Tripods can be sold with legs only or as a kit with a tripod head. The following links are to tripod legs only.
The tripod head is the all important link to the tripod legs. It is the mechanism that you will spend the most time manipulating. If you don't like the head you get, you are far less likely to use your tripod. Although Gitzo is the Pro Standard for Tripod Legs, I am not a fan of their Tripod Heads. I prefer Manfrotto (less expensive) or Acratech or Kirk (more expensive). I recommend getting a ball head that supports at least 15-20 pounds. If you often use longer lens than I recommend the 20+ models.
Most folks like the convenience of Ball Heads. Smaller Ball heads will be lighter but won't support the use of long lenses. Larger ball heads will be more expensive and somewhat heavier, but will be necessary for long zooms or long fixed lenses. I use a Acratech GP Ball Head. One of the lightest and strongest, its great for speed and weight. When absolute precision is necessary I use a the Manfrotto 410 Junior Geared Head. This is a much heavier tripod head but brings absolute control.
There are countless filter choices for the photographer. Multi-Coated filters will provide a higher quality light transmission than the Single or Non-Coated filters. For filters that I use regularly, I purchase the Multi-Coating.
A similar argument can be made for the manufacturer of the filters. I find that B&W, Heliopan and Singh-Ray make very high quality filters. Tiffen and Hoya are less expensive alternatives.