Build a megabase that has everything under one roof, including a guardian farm! As a bonus, there's a mine shaft under the ocean monument.
Most of the small island is in range of the elder guardian's mining fatigue spell, making it extra challenging. You will need to visit a nearby island to get a cow for milk.
If you build a nether portal at or very near spawn you will enter the nether about 50 steps due north of a nether fortress, and around 100 steps from a blaze spawner to make a very convenient blaze grinder for XP for your mending items.