What does premium currency buy you?

Currently the marketplace allows you to buy the following items with GC (the currency that can be purchased with real money)

• A very limited range of ammunition for a select few guns
• Mele weapons
• Medical supplies such as vaccines and medkits
• Food and drink
• Various weapon attachments (such as scopes and grips)
• Cosmetic items (such as hats)

You can also buy some mele weapons and medical supplies using dollars (a currency that can be collected in-game), however the selection is more limited. I'll try and post some screenshots later on.

For what its worth players who choose not to buy items from the marketplace do not appear to be massively disadvantaged from my play experiences so far. Clearly there is a benefit to players who buy items from the marketplace however all of these items are available as loot in the game world (although I've not spent long in any of the military areas so I'm yet to find any scopes).

If you are referring to gold coins, you can purchase cosmetic items such as various apparel and cosmetic customizations, chem lights, and flares. You can also buy clan member slots. Source