Returnal is a tough game, but its difficulty is reasonable and success is more than possible if you understand the mechanics, here’s few tips:
1. Health is your most important upgrade. A large health pool can absolutely be the difference between victory and defeat. In order to maximize your success here, it’s important to understand how resin works. 3 resins are necessary for one small health boost (2 if you luck out and come across the expensive artifact, which IS worth the money) and pure resin can be rare to find. However, if you are at full health, every health pickup will turn into resin.
So it’s a good idea to spend your time in the first biome (or fourth if you’re in act 2), clearing out as many enemies as you can on the map, without picking up health items, then get to full health using the bed in the Helios ship (or using as few items as possible).
At that point you can do a “health sweep” and pickup every healing item, boosting your health significantly. Then and ONLY then, use the Integrity augment machine, which will be in that biome’s fabricator room, because it will boost you by an additional 25%.
2. Ether is confusing and rare in act 1, but plentiful in act 2 and it is EXTREMELY valuable. It is one of the few things which carry over between runs and it caps out at 30. Having 30 ether going into a serious attempt at the final boss will help a lot.
The most obvious thing ether can be used for is nullifying malignancy on items and chests. Meaning you can spend between 2-5 ether to remove the risk of valuable items giving you suit malfunctions.
However, there are two far more critical reasons to have ether on hand. The first are the exchange stations which are near the fabricators, which can transfer Ether into 200 obolites, giving you the money necessary to buy valuable upgrades and items before advancing.
Getting a Space Man figure (instant use extra life), Large healing pack and the health augment I mentioned above, can all be the difference between victory and defeat- and you may not be able to organically find enough obolites in each stage to buy them all.
The second reason to hoard Ether is to activate the Reconstructor in the final biome (or whichever biome is giving you trouble).
This machine is effectively the closest thing this game has to checkpoints. So if you die, you will be resurrected at that point, with all enemies you’ve cleared since activation still dead, all the consumables you’ve used still expended.
You’ll also have full health. I used the reconstructor in the final biome on my successful run and considering where I died (while crossing the bridge to get the key to the final boss room) I would’ve been furious if I had not used the reconstructor.
3. Weapons unlock perks over time (permanently) as you use them, and they increase in power on drop as you level up your proficiency in each run.
Waiting until a biome is mostly clear to open weapon chests is a good way to get more powerful drops and have options as to which one you’re going to take.
I swear by the Hollowseeker and used it on every successful boss kill in the game. As I used it I unlocked incredible upgrades which were extremely powerful.
Have fun and say a prayer you don’t run into any glitches – I had the sound completely drop out during my successful final biome run which kind of killed the experience (and I’m amazed I was able to kill the Elites in that stage without sound, let alone the final boss), so I hope you have better luck than I did!