There are a few places where you can track and validate what Gear Packs you have unlocked, and which are still locked.
1. The "MY ACCOUNT" Section of the Gears4.RockstarEnergy.com website.
2. Log into your Xbox Live account, and navigate to "MY GAMES" this will display your unlocked Gears of War 4 Gear Packs.
Additionally, when selecting the Gear Icon, you'll have the option to Group By: RARITY, CLASS, TYPE, and ONLY OWNED CARDS
Horde Bounties >>> Common = Rockstar Challenge & Rockstar Horde
Versus Bounties >>> Common = Party Like A Rockstar
EPIC >>> ACID, GODMACHINE, HERNANDEZ & HYDRO
LEGENDARY >>> GODMACHINE, HERNANDEZ & HYDRO