In reply to Davy Murphy:
If I was you, I wouldn't want to buy cams based on a single type of rock, I would want to have as versitile a rack as possible.
I am not an experienced climber but I thought I will chip in with what I have found from using my "beginner rack". (I have just returned from Tryfan last week-end ,climbed overlapping route and gashed crag: Easy, friendly rock, lots of protection opportunities, used lots of spikes, some nuts and only one cam placement (for convenience more that necessity)
At present I do mainly multipitch, low grade routes to around VDiff (more mountaineering than climbing). I like to use passive gear a lot. I only have 4 cams, ranging from 10mm to 80 mm, all of different makes, bought at bargain prices when on sale. Useful at times but, at the level I am climbing, not indispensable. I also still climb with one rope and didn't really fell the need to get two half ropes yet, as long as I make good use of extenders.
I personally feel that climbing in this way will give me a good apprenticeship that will set solid foundation for harder climbing. I am more and more proficient at placing nuts quickly and precisely, at making the most of what the rock can offer, etc...
Cams will become important, eventually, but there is a lot of climbing that can be done without (or with just a few).