The Gunbucks are one of the in-game currencies. They are used for buying and upgrading Weapons and Armor in the Arsenal. Also, you will need Gunbucks if you want to create a Clan or buy some of the Special Offers in the Store.

You can get Gunbucks for completing the Daily or Main Quests, by opening the Crates, winning the Battles, or you can buy them it the Store for Gold.