All I did was abuse explosive and toxic arrows. The only time I entered melee was for a silent kill. You really don't need to go out of your way to get xp from collectibles, just grab what's in front of you, and be sure to collect as many resources as you can. Loot everybody ofc. You'll need wood for camps but I was still flush at the very last one. Save points aren't that far apart, you're more likely to fall from a bad jump than get hit by enemies. Once I died because I couldn't swim fast enough. Also, just sprint past the cougar to the right and up the stairs in the Flooded Archive. At the end of Research Base just keep popping up from the water and shooting off a toxic arrow, then dive back in and swim in the opposite direction. Do this a few times and you'll be cake.
Make your first or second skill upgrade the bonus xp. I ignored anything relating to animals. I didn't buy anything with coins until the last time I was in the area and all I got was a silencer for the pistol.
The only optional tomb I did was Voice of God just for insurance. I had to manually heal maybe twice in the final battle, if not from gunfire than from fire on the ground. Took 2 and a half sessions, maybe 7 hours if you hold down shift. Knowing the routes from my first playthrough and also score attack definitely made it smoother.
For outfits I used Apex Predator for the bear, then Huntress (or anything that reduces the delay before health regens like Sacra Umbra, Ancient Vanguard, Commando, Infiltrator, etc.), then Shadowrunner once I started shooting people. Any gun will do just roll with what's comfortable. I lightly tapped the ak and saved the shotgun for the dudes with helmets and armor.
Oh yeah, make your life easier and set all the gfx options to low, your game will look wack but you'll see everything, there are zero shadows.
hf!