OMG it's so difficult deciding what to buy that you actually need and will use.
Marcus, you're not kidding. The usual rule is to workout the range of focal lengths you need to cover and then pick an assortment of lenses to cover that range. However, when you're shooting certain subjects you often need something more specialist than a general all purpose lens, such as shooting sports action in poor light for instance, or for doing portraits or close-up/macro work. Again, sometimes you can use a specific lens to do both of these, such as portraits and macro with an 85/90mm lens on a cropped sensor or a 135mm on a full frame sensor.
Things to consider before buying lenses
So firstly have a look at what specific subjects you will be shooting, such as landscapes, sports/action photography, portraits, wildlife etc.and identify them.
The think about what the light levels will be like to determine the maximum aperture you'll need and how shallow your depth of field might need to be
Then look at the market to see what lenses are available that will cover the focal lengths you need with the widest aperture you need, at a price you can afford
Read the reviews on each of the lenses you select and also ask around on the forums to see what other people who already have that lens think about it and how it performs.
Go to a camera shop and try the lenses on the camera body you will be using to make sure you're happy with how it handles and the build quality.
Check the market again to see what the best deals are, from reputable dealers only, so research those as well before you finally make your purchases.
