I recon for your average bloke a good start is a fish. There are lots of types for small waves and you can generally find one that would suit you.
Then go for a standard shortboard. Now these days there is many different types so you can really find something that suits.
Then maybe a step up depending on the waves you are surfing.
I think most people could get away with 2-3 boards. At the moment Im have three.
Two 6,3s and a 6,8. I really need some mid ground although the 6,8 feels great in any size wave and that really was a suprise