Valt, you actually buy Mc with real money, and then use them to:
Buy Hero Mechs that earn more money
Or normal mechs, but for those you can use MC (real money) or Game Credits which you earn in game with fighting called CBills.
Or you buy storage space. These are called Mech Bays
Or you Convert XP, which are only usable on the mech that earned them, to GXP, "General XP", which you can use to buy modules or:
On a mech you don't want to drive but need to unlock something called Pilot trees. Pilot trees offer benefits unlocked with XP or GXp and enhance the performance of your mech. Since for every 100 XP you only get 5 GXP for free, that can save you a lot of time grinding. At 400 XP a game you would need to earn 300.000 XP to unlock even one module for free, or around around 100 hours.
Edited by Hammerhai, 14 September 2013 - 01:07 PM.