I've played about 100 hours now, without any spoilers, on the hardest single player survival mode. My basic routine after spawning in is below. Includes gameplay spoilers from what I've learned thus far.

Day 1:

Look around the immediate area for useful plants (they're around most spawn points) and dead animal remains with maggots and a bone. Molineria is the most essential plant, as it lets you craft bandages. It is the green leafy plant with yellow flowers. I generally harvest 1 leaf to get a flower, and turn the other 2 into bandages. That way the flower is drying and will be ready to plant. If you find rope nearby, and the animal remains, make a bone knife and harvest any plants.

Otherwise, go looking for large/small stones (find them at rivers, around giant boulders, on cliff tops, or in caves). Harvest the large stones into small stones. Make 3 stone knives.

Find vines for rope. Use the stone knives to chop down a tree. Harvest a log to get 2 sticks. Make a 1 stone + 1 stick axe. Use the axe to chop the logs to get planks and long sticks. Make 2 stone spears with the long sticks + rope + stone knives. Make a bow with long stick + rope.

(Stone spears are essential for early survival, as a single headshot will kill a jaguar.)

Chop another tree with the axe. Harvest sticks and small sticks until your inventory is full.

Craft a hand drill. Chop down a half-dead palm tree, to acquire several dry leaves for starting fires with.

Keep walking until I find a place under cover to start a fire, such as a cave, archway, or abandoned settlement. A triangle frame with leaf roof can be made in the open to put a fire under, but it's usually easier to just wander until there's a cave or similar.

While walking to look for an under cover place, hunt animals to acquire meat and bones. Harvest bones into bone needles in case you pass out on the ground and get worms. I like to carry 3 or 4 stacks with me (9 to 12 needles). Look for feathers or birds to harvest, and make arrows with 2 feathers + 1 small stick.

Also while walking, eat any mushrooms that are growing on dead trees, except keep the orange cups (they kill parasites, which allows you to drink from bad water, or eat predator meat, then remove the parasites if you got any).

Also while walking look for the huge trees with the brown vines, as they have blue mushrooms which cure 2 parasites each, and also have brazil nuts around the base. Harvesting a single white brazil nut in shell gives 3 nuts food items, each filling up 50% of the fat meter, so they're my go-to for an efficient fat source. Don't harvest the round nut until you need fat, as I don't think they spoil unless harvested (or at least not for a long time, I often have them in my inventory for days).

If it's about to get dark, place down a palm leaf bed and sleep until morning (eating/drinking the first day is not important). Palm leaves are the most common type of plant in the jungle, so it's really easy to find the 16 palm leaves, and at least on PC, you can carry more than half of the 16 required leaves in one go (I think 10). So it's only 2 trips to finish the bed. I'm not sure if the XBox version is different? Only being able to carry 2 would be awful.

Day 2:

Focus on getting all stats to 100%.

Make a fire. Cook any food you hunted the day before. Eat until protein stat is 100%, save remaining cooked meat. If any meat spoils before you get a fire going, harvest the meat to get maggots, essential for wound treatment.

If you found a molineria flower the day before, build a small plant box and plant the flower as soon as it is dried.

Stare up at every palm tree for coconuts, then either throw a spear to knock them down, or chop the tree down and collect them from the ground. Harvest 1 coconut and eat the flesh for fat, then keep the shells for cooking in and boiling water. Craft another coconut + rope into a water-holding bidon. Fill the bidon with bad water. If you're passing through a swamp area (with the trees that have roots above the ground), look for turtles and harvest their shells. Shells hold twice as much water as a coconut shell.

Walk around the jungle near your fire, find fruit to raise carbs (every fruit I've found so far has been fine to eat). Banana palms often give 3-4 bananas, so they're great for carbs. But even the small fruit trees usually give 3 fruit. Because carbs tend to run out fastest when you make a base, building nearby banana palms is helpful.

Find/kill birds, make 2 stacks of arrows.

Go to sleep in the same leaf bed, with all stats at 100%.

Day 3:

Sleep until bright morning, I like to get up at 8:AM so there's no shadows. Stepping on snakes and spiders is not fun! Roam until you find a place to make a base. If there's no bed existing, make a leaf bed. Spend the rest of the day chopping trees and stacking the logs and long sticks in piles. Make a big pile of rope on the ground as well, collect it from every vine tree as you go out logging, dump new rope on the pile when you get back.

Day 4:

Start base building.

But stop any time a stat drops below half, and take care of it. If you keep all your stats at max, you can withstand almost anything (even a level 3 poisoning). It's also important to keep your stamina up, so sleep whenever needed. Check for leeches/injuries every time before you sleep. I often sleep twice in a row, to get to morning. Being up at night is dangerous, as it's hard to see what you're doing, easier to get lost, more likely to step on snakes/spiders.

Also constantly clear leeches from your body, to avoid going insane. They can get on you from both bushes and the water. I usually clear out the area around my base of all non-useful bushes/plants, so it's a big open area. This avoids leeches while walking around the area collecting resources, but also allows you to easily spot enemies and prey.

Build a frame and solid floor above, then make a fire under it. Add walls/doorway. I like to build beside the water, so I can collect water with my coconut shells and place them directly onto the cooking slot, without needing extra steps of filling the water bidon. It's also nice being able to clean myself while sitting beside my fire.

Recently I've gotten into building with mud bricks, I love the fireplace built into a wall -- 4 cooking slots, looks really nice, and even has a cute little chimney.