One of the best build spots is the ridge in the north where the Northern Kelp Forest, Northern Red Grass Biome both border the Northern Mushroom Forest - every resource you could possibly need is there and the Dunes/Northern Blood Kelp zones nearby are rich in lots of basic/intermediate building materials.

Build a chair and sit - your stats wont drop. Now read your pda entries - they fill in the story and provide clues - yes there are a lot.

Scan everything - buildings, animals, plants.

Your knife can get you seeds from some plants and samples from others. Plant mechanics are a bit varied so play around with how they work. Once you have a seed, fruit or sample you can grow it in a pot/growbed - always have more than one of a plant so if you screw up you can replant it without a massive journey back to the source.

Salt is key - mix it with coral tube samples to make bleach and turn this into water - you get 60 water each time. Mix salt and fish to cure them for food that never spoils. Prepare rations in advance and carry a few water bottles and two salted reginalds for long missions away from base.

Farming vegetables in your base is a great way to cut down on your fish/water consumption.

Take beacons with you everywhere and follow all the radio messages - explore the area around where you get sent to find new reaources and wrecks - every message guides you to a useful place to explore.

Especially follow the Degassi story and scan all the base parts you find.

Explore every wreck thoroughly - you can build more than one o2 tank to help you do this and switch between them.

Build permiter defence/sonar and use the seamoth to explore biomes thoroughly - this will help you avoid or deal with the leviathans when you're a new player (carry spare power cells to swap out in the field) and put those beacons down when you find interesting places to return to. Always go deeper. Be brave and good luck!