Killing monsters will drop more Maple Story mesos and expensive items that cost more than your pots. Mages have Mp Recovery which allows you to stop wasting pots and save MapleStory mesos but it certainly does not save time, so you should also take advantage of your skills for Experience.
Buy low and sell high strategy is commonly used by many MMORP gamers. It's lucky for you to meet noobies selling their items in a very low price which actually worthy more. If possible, bargain it out, buy in with a really price. Then sell it out to make a profit. If you are buying items, you should look for the people that been trying sell a certain item for a long time. Since they are mostly easier to persuade, bargain like crazy.
Hunting is important but takes risk. It might make you lose MepleStory money or gain tremendously. Things you need to hunt are easy to kill but drop Godly items.
Equipment in Maple Story is very important. During low levels you should skip equipment in order to save but during high levels it is not worth saving a few millions in order to save those milloins, because you will waste that amount of Maple Story Mesos on pots. You are leveling faster and more efficiently thus using less pots and saving Mesos.