imho i think hardest is mining, agility, thieving because you cant buy exp for this skills slayer is second because you travel al the world, not only one location and u can half buy exp with cannon, or guthan, super sets, or other stuff herblore, prayer, rc, smithing, are all about money if you have 100M + it isnt very hard like mining or agility fishing, wc are afk skills, so it isnt so boring and the easiest are fletching and cooking cooking is fastest skil ever next is prayer, yes prayer is very fast, but u need much money fletching is fast too, but stringing may be boring