Lara has 7 inventory slots:

• Weapon
• Two ammo slots (note: the two ammo slots are interchangeable; however, there are more ammo types than slots, so you won't get full coverage)
• Bracelet
• Ultimate attack
• Backpack
• Necklace 
• *Outfit slot.

How do I obtain gear? 

You can buy crates and other loot packages in the store. Want free gear? Here are the ways you can obtain free gear:

1. You can get one free ordinary crate that will drop a common or uncommon gear item per day. Access it in the shop.
2. Enemies will drop gear after killing them sometimes (although it's extremely rare)
3. After you complete a world, the wheel spin you get has an ordinary crate as one of the slots, so it has a chance to drop.
4. Completing your daily dash objectives every day. You will be rewarded with a weekly dash crate, which could have gear in it.
5. Buy premium currency crates in the store with the premium currency you obtained for free while playing the game.

There are 4 rarity types:

Common, Uncommon, Rare, Epic. You level them up by spending coins and manuals. The number of coins and manuals it takes to level up a gear item increases as it levels. Common items max out at level 20, uncommon at level 30, rare at level 40, and epic at level 50. On top of having a higher max level, the rarer version of the gear (eg uncommon over common) will also have a better base stat (eg a level 20 rare will have better stats than a level 20 common). It can also have better passive abilities (eg better dodge chance) and sometimes additional ones.