The best method to gain Experience Points (XP), which are necessary for leveling up your Battle Pass and unlocking all those new skins and cosmetics, is to complete the weekly tasks in Fortnite Chapter 5 Season 3: Wrecked.
Every weekly challenge offered so far is listed in this guide, along with advice on how to finish them efficiently. As you complete each task, you can check it off, and your progress will be saved!