Give and Take
Once you have decided what your needs and budget are you can start to chose your lens or lenses. Some people only want 1 lens and chose something like a Sony SAL18250 (DT 18-250mm F3.5-6.3, versatile wide angle telephoto lens with 14x zoom range for crop format cameras). If you chose a lens like this you will have a great zoom range in a compact lens, a good choice for travelling or general snap shots, but you will have to make a compromise e.g F3.5-6.3 isn’t that great for low light performance. Portrait shooters may choose Sony SAL-85F14Z (Zeiss 85mm 1.4 Zeiss ZA Planar T*), a fantastic sharp fast lens, the down side being its price, weight and some may say focus speed. The most important rule when lens shopping is don’t be cheap you will only regret it latter, a good lens will cost you but it should be a one off investment that will last a long time.
Mix and match
There is no perfect lens collection or solution. In fact the more you buy the more you want, which can cause a major stress on your wallet. At the moment I have 19 lenses that I use (and more that are just there in the cupboard) on either a regular or semi regular basis, ranging from 14mm to 1200mm. IMHO most people could use 3 lenses for best results. Two of them are standard lenses and that suits your shooting style.
• A standard zoom, preferably with a constant aperture over the zoom range . e.g SAL 2875 2.8, SAL24105 3,5-4,5, Tamron 17-50mm 2,8 XR Di II LD ASL, Tamron 28-75mm 2.8. Then there is the top of the line Zeiss SAL2470Z. All these lenses are full format except the Tamron 17-50. All these lenses are constant 2.8 aperture except the SAL24105
• A 50mm. If you only ever own 1 prime lens make it a fast 50. Some people don’t like them but I think they may be because they just don’t get it. They are sharp fast and light e.g SALF18 crop format f1.8 cheap, Minolta 50mm 1.7 a loved classic, Sigma 50mm 1.4 not the cheapest lens but may be the best 50mm on the market for the alpha mount at the moment
• A lens for the things you want to shoot the down side is they tend to be specialised lenses and cost a bit more (I never said photography was a cheap hobby) . e.g macro, ultra wide, or telly. If you want to get down low and chase bugs or flowers do it get a macro lens SAL100M28 is an amazingly sharp macro lens or a SAL30M28 a crop format macro lens at a good price. If you want to have some crazy wide angle affects look at some of the ultra wide lenses e.g Sigma 8-16mm F4,5-5,6 DC HSM (crop format)