As for my opinion campaigns of course and somewhat mining if you have a possibility to get an equipment for the mining. Otherwise campaigns will be the top and of course some will say gambling but that's just not mine. Last campaign that I followed from DexAge wasn't hard I'd say, just do the following requirements and you're all set like any other campaign. Gambling in other hand can be more profitable but at the same time you can lose a lot. So it is up to you if you like risk or stability.