On my main world, I combine fighting, trading and farming. So far - to HMA - with fair success. However, as soon as the Summer Event is over, I will be increasing the GBs from 3 to 6 and I suspect the shortage of space is going to force me to specialise more.
Oddly, the other worlds seem to be almost deciding for themselves which way they are going! On beta, I will just mess about, though, as I created a town there for test and information purposes so I'll be messing about and occasionally (almost) wiping the town and re-building.