Let me tell you what lenses I own and we can take it from there:
- 50mm prime for portraiture in the open and indoors where I need to capture more light. It's fantastic and I just love the bokeh. Tips on outdoor portraiture with samples - click here.
- 18-55mm kit for when I need to go shooting at weddings (I shoot with this lens at tables). You just can't go without a vario for such events. I prefer this lens because it's cheap, it's stabilized, I wouldn't care bumping it occasionally and performs rather well in cases when sharpness is not that important. Tips on wedding shots at tables - click here. You could also go around town shooting buildings or mount it when you want to break away from the concrete and take some nice nature shots (flower photography tips here). It's wide and will provide a decent vario range.
- 500mm mirror for the beautiful doughnut bokeh that is unique to this type of lenses. It's really fantastic even though the lens is not sharp it will give you unique effects and make people wonder how you did that. To be honest, I don't really use this lens so often.
- 85mm prime - the bokeh is just fantastic and the sharpness is a wow.
- 24-70mm - really sharp and the aperture is wide open. What I really like about this lens is that it's also fantastic for studio shots where you not only need the vario but also the sharpness. Speaking of studio you can check my backdrop tips here.
- 80-200mm or 70-200mm at 2.8 - we all just need a long range lens from time to time so why not get a really decent one. This one is not on the necessity list because it's heavy and big. You can't just carry it around always and you need more space to take photos with it. Once you get it though you will want to keep it.
- Prime lenses will give you great sharpness, beautiful bokeh and lots of light. You will be shooting with such lenses mainly outdoors where you have plenty of space. Get a 35mm prime if you want to shoot in tighter spaces as well. Also these are less expensive, lighter and focus very fast.
- Vario lenses are pretty much universal and are perfect for the casual photographer who likes the dSLR quality of image. If you have a higher class vario you can really use it for anything. I am talking about the 2.8 aperture lenses. You can shoot in a studio, outdoors, indoors... pretty much anything. Note that these are expensive but for a very good reason.
- Know your camera. If you own a full frame camera make sure you're buying full frame lenses. Cropped sensor cameras, on the other hand, can use full frame lenses just fine.
- Know what you want to shoot. Most often people buy something because they were told it's good. I like my 50mm because I like getting the details and I use it every day. Some people are really enjoying landscapes and will need a wider lens starting at 18mm (or wider) and won't need an aperture starting at 1.8 for shooting mountains and rivers.
- Get a tripod for the long lenses. You will need it especially in poor light conditions.
All the best,