Using the Auction House
In Maplestory 2, The easiest away to buy stuff is via auction house (also sometimes called black market)

to open up the auction house window:

Click on the Auction house icon from your menus or Find an auction house ncp

Selling

Buying

Input info on the stuff you are looking for. here are some of the stuff translated.
If you click the item name box, you can search for items by name. (You can copy paste Equip names)

After you got all your search options selected

pick the item you wanna buy and hit the buy button, and then hit the confirm button. Items are sent to your Mailbox!

You can also Buy Mesos with blue merrits(just hit the mushies option and hit search)