What is the best class for base 19?

It depends on your play style. If you enjoy attacking and have time to spend scouting out enemies and raiding them for resources then be a Raider. A Trader will have better money production and lower resource needs, but you will be vulnerable. Farmer is safer as you have some protection or your resources and fairly good production speed.

Probably Farmer is best for the casual player trying to upgrade, Raider if you play a lot and want to fight.