You have a grueling adventure ahead of you, but you can start things off right by keeping the following tips in mind.
Keep the different modes straight and play in the one that suits your interests. You lose gear if you die in Adventure mode, but in Exploration mode, that penalty doesn't exist.
Stick near the beach until you're truly ready to start exploring. You should level up your backpack so that you can hold more stuff (food especially), and piece together some weapons and leather clothes so you can survive combat.
Make sure that you're ready to fish almost immediately. That will help you avoid dying from hunger. To craft a rod, put together 2 pieces of string and 3 pieces of wood.
Pay attention as you wander, since you'll find items that are useful for crafting essential equipment. In particular, watch for opportunities to gather twigs and flitn, fiber, leather, leaves, and the various types of ore.
Try to master ranged weapons, so you can deal with your foes from a distance and with minimal risk.
Campfires
If you do not have torches, you can make a campfire to keep predators away at night using the twigs that you gathered.
Fat
At times animals will drop fat. It can be used as food or to build torches (recommended). Eating fat is a waste of a required resource.
Meat
Killing animals to get a chance of collecting raw meat. Instead of eating it immediately, spend some time to cook it to refill your hunger meter more. To do this, get the required resources to build a furnace. Use twigs as fuel, then set down the meat in the furnace next to the fuel.
Storage boxes
After creating storage boxes to hold supplies, place them in hard to reach locations. The boxes can be broken accidentally with a weapon while fighting off animals.
Tower Codes
Around the island, you'll find towers you need to access. The access codes for those towers are provided below.
161803 - Central Tower
214808, 534211, 628620, 706798, 803482, 899862 - West Island Towers
097494, 419716, 459230, 510582, 781640, 939937 - East Island Towers
846264, 950288, 979323, 265358, 314159, 338327 - South Island Towers
Weapons
Explore the ruined buildings found on the island for supplies and weapons. Do not keep too many weapons on your character at one time. You will lose any weapons you have when you die. Leave your access weapons at your home camp to always insure that you are armed.