well depends how much cash you have :P if you have 7b you can get 99 construction in one day. but im going to guess you dont, easy 99's that are quick are: woodcutting, firemaking, flecthing and cooking. these you can get any in a week. some skills i dont recommend you even try, like rcing or slayer or agility. if you want a respectfull one and have some cash, go for smith. you can make money eventually through it.