The economy on the server is backed by Diamonds. Each Diamond has a value of $100. You must manually convert your diamonds to money to be able to use them at shops and you are also able to convert your money back to diamonds.
The area where you can do the Diamond conversions is at /bank. When you are on the server type /bank and you will be teleported to the area in the image below.
How to get money
Once you are at the area below (type /bank in-game). You can use the shops in front of you to swap diamonds to money or money to diamonds. Left-Clicking the sign on either of the chests will let you use the shops.
The chest on the left will let youchange your money into Diamonds.
The chest on the right will let youchange your Diamonds into money.
Commands to remember!
/bank - Teleports you to the money conversion area
/balance - Shows you how much money you have
/shops - Teleports you to the shopping area