The quality of your photography is governed by a number of things, but the single most important aside from the ability/skill set of the photographer is the lens. There are amateur lens and professional quality lens, and the price will reflect this. One lens that is a real value out there is the Tamron 28-105 f2.8 lens. I had one and sold it, I often regret it. That lens is not quite as good as a Canon or Nikon lens, but it is very close, and if you can find a used one for sale, (very difficult), you can sometimes get them for R1500 to R2500. Highly recommend this lens for the value it delivers.
The maximum aperture size of the lens is a very good indication of the quality of the lens. All of my lens now have a maximum aperture of f 2.8 though out their focal length. All of my lens are full frame sensor compatible as well. My cheapest lens is worth R2,500, that is the downside, but the lens is the single most significant limiting factor in the quality of my shots. I could be the most amazing photographer with the top of the line camera, my lens will limit the quality I can produce. The lens is what limits the sharpness of the photo, the color of the pic, and often any distortion around the edges of the pic as well – all determined by the lens.
For those of you who are committed to being professional photographers one day, buy the best lenses that you can. Camera’s depreciate in value like cars, lenses do not. Try to buy full frame compatible lenses as when you do make the move to the full frame sensor camera, then you will have to purchase all new lenses all over again. If you know that you are never going to go the full frame sensor route, then you can get away with the cropped frame sensor compatible lenses, but they will not give you quite as good of quality.
On zoom lenses be careful of the f stop, some have an f stop that will read f 4-5.6, meaning that the maximum aperture will change from f 4 to f 5.6 as the focal distance changes. The value of used lenses remains pretty constant, so if you buy a good used lens today and want to sell it in a couple of years, chances are you will get most of your money back. I just sold a Canon 35-350 mm lens for R1200 more than I bought it for about 2 years ago.
In summary, I recommend not to go cheap on lenses. Try to by lenses that are compatible with full frame sensor camera’s for the best quality. An f stop of 2.8 or less will ensure the absolute best quality but probably the most expensive as well. If you can only afford lens with an f stop of 4 that is okay, but try to stick with the full frame sensor compatible lens if you are very serious about the future of your photography. If you are just an avid amateur and that is all you ever want to be, then these recommendations may not be so important