The in-game shop is accessible at your team's fountain. Here, you'll spend gold earned from farming minions, killing champions, and taking objectives to purchase items. Items provide various stats like attack damage, ability power, health, and armor, and often have unique active or passive effects. Building the correct items for your champion and against the enemy team composition is a critical skill. The shop offers recommended items, but learning to adapt your build is key to success. Don't be afraid to experiment with different item paths.

The Shop and Itemization — League of Legends Walkthrough