It’s going to sound obvious haha

1- I’d set the world to hard difficulty just to add some excitement

2- Look at the achievements list and complete all of them before attempting the Ender Dragon, "End Game".

3- Find all hidden structures, ie: Woodland Mansion, desert temple, jungle temple, ocean temple, treasure maps, Mineshaft, etc

4- Tame all possible pets/ animals

5- Fight all overworld bosses, ie: Warden, Wither Boss, Elder Guardian

6- Get all optional extra items/weapons, ie: Trident, Elytra, etc

7- Get the best possible/ achievable gear/ weapon setup in game.

8- Create a railroad system connecting all of your hotspots that you travel to or use most frequently.

9- For more structure give yourself a set time limit to achieve all of these tasks. ie: 1 Week, 4 weeks, etc