I have now leveled up tradeskill to 300 as an experiment.
I didnt use any sploits, but legit trade.
Basically I bougth mules for 20 denars at Askar and sold at different towns for 60-200 denars.
This is the most boring skill-experience I have ever done in the game, I cant express how boring and grindy it felt.
as others this skill needs a much faster progression.
Basically the main purpose of actually leveling up fully to 300 is the ability to purchase towns, which imo should be placed way lower down 175-200 at most.
So "casually" you can be able to do it.
As others point out give more sources.
Any sale should give you xp even if its not profitable, that would most likely help out alot.
Specially in terms of selling looted item.
Workshops/caravans also should give you passive xp perhaps.
And overall ask yourself this, is it a good mechanic when ppl go to look up exploits on how to lvl up fast or do it mean that it needs more work/improvement.