XP is something you can earn in both God of War (2018) and God of War Ragnarök. It's as simple as it sounds at first, but used quite differently in both games. You can earn XP for Kratos, Atreus and Freya in God of War Ragnarök, as each character has their own XP pool.
General information
There are two core features when it comes to the leveling system in God of War Ragnarök: XP and Gear. Leveling gear in God of War Ragnarök requires you to obtain components and crafting materials that are used for making Kratos' weapons such as the Leviathan Axe or the Chaos Blades more powerful.
While you will earn XP as you complete quests and combat gauntlets in God of War Ragnarök, it's not used to level up. XP is instead required to purchase skills and upgrade select equipment and gear. In order to level up you'll need to upgrade your gear by either discovering new armor and attachments, or by crafting improvements to items you already own.
You can craft upgrades using all resources at one of the Huldra Brothers' workshops, and these are located in various places across the Nine Realms. Keep in mind that different gear impacts your statistics in different ways. You'll be shown a visual representation of how a particular upgrade will affect Kratos' stats before you purchase it.
You can find your current level by bringing up the inventory at any time, or at one of the Huldra Brothers' workshops. Your current level is the big number in the top-left corner of the screen. Make sure this number is either the same or higher than the enemies you're currently facing, otherwise you may find you're underpowered and ineffective in combat.
God of War: How to Earn XP
Succeed in Battle
The easiest and most obvious way to earn XP in God of War is to have success in battle. Unlike other games, you'll only unlock XP once you've beaten every enemy in a combat gauntlet, so make sure you clear everyone out before moving on.
Complete Favors
Favors in God of War are essentially sub-activities, and they span a variety of tasks. Some of these are full on side-quests, while others require you to complete simple combat objectives or find a set of collectibles named artifacts.
Progress Through the Story
Similarly to favors, you'll earn XP as you complete story-based quests.
God of War: How to Maximize XP
If you want to earn the maximum possible amount of XP in God of War, focus on increasing your luck attribute by equipping appropriate armor and enchantments. This will increase the amount of XP you earn per battle, thus enabling you to upgrade your gear quicker.