Can you tell me which class is best for growing quickly?

This will depend on how you play. At the low levels the builder class is very useful as it lets you get through some of the low level building stages very quickly. Trader is not the best I think for quick advancement.

The other 2 choices are raider and farmer. Farmer is best for production and gathering so if you are a peaceful or less active player then this will be the quickest. Raider has lower production rates so can be slower unless you play a lot and enjoy the attacking / kill events and other PvP activities. In this case you will be able to gain more from attacking enemies and can potentially advance faster, if you are active.