How to improve your class?

I made my way to 68 (osa) basically doing quests/ missions... To be honest I am not a fan of solo fighting. Kwistmas is giving good exp and I think you have enough lvl to do at least some of it.
As for money, sell everything (some loot is worth nothing, some is worth quite a bit), not just wheat (actually, don't sell the wheat, if you are desperate for money and like the crafting system become a baker and sell bread). Also, I never had my full gob set.... As I said, I was doing quests, so and some random pieces of equip were enough until I bought my Jelly set... I am still not 100% sold on it, I am sure I need to swap out some pieces for better versions.
Dungeons give good exp (specially the first time if you manage to hit some missions), but you probably will need to ask for help (sometimes just waiting at the door is enough.... More often you need to bring your own group).
Everything else... There is really no secret. Get better (read - more expesive) equipment, invest your points in characteristics and spells...

That was my experience, anyway. Hope it gives you some ideas.