you need both of them, as Kirsten said, you see lot of people starting to buy items than hiring mob, but Id suggest, first finish off hiring mob while you're adding mob, this will allow you to be much stronger than people in your range, you can win fights easily, so that xp is helpful to level up. of course you need to allocate items to 2000 mob as well, in order to be effective. Boss drops are the best way of an opener to get stronger. make some highlevel friends
And always remember MOB is one of the most important factors of the game.... I wish they would increase the mob size after level 5000. And then again after level 10,000. I know, most probably would disagree as it was hard enough to get to 2000. lol
