In reply to 1poundSOCKS:
I agree regarding the size 3, much to my climbing partners chagrin I take a size 3 on most multi-pitch routes and use it fairly frequently. Ideally, i'd suggest the OP saved up and bought 5 (0.5, 0.75, 1, 2 and 3). I couldn't bring myself to suggest just 3 and miss out the size 0.5 (It's probably the bit of gear i've had the most 'thank god' placements with)!
I think all of my size 4 placements have been more a case of 'I can't be bothered carrying this anymore' rather than actually being all that useful! Although it's nice to have for those worrying routes that say 'large friend essential'.