Biomutant's a weird one. It's not a great RPG, but its world is definitely worth seeing someday, though I'd probably wait for a sale. If you're already committed, I have some crucial Biomutant tips for having the best time possible in its beautiful, shallow world. You probably won't need any help getting through it since it's not very difficult, but you might need some help having the best time possible.
Play on hard
It's the only way to squeeze some good pressure out of the gear system. Normal difficulty will rarely throw a challenge big enough at you that you'll need to dip out and find some new armor or whip up a new weapon, so turn up the heat a touch. Hard difficulty still isn't too tough, especially if you're spending a lot of time exploring. There's such a glut of gear out there you'll eventually accumulate enough junk to roll over any threat, but you might delay the bottom falling out a little longer.
Don't agonize over picking your class
Biomutant makes you think it's going to be a class-based RPG, but the fences all fall down the moment you hit the road. Gear is rarely stat-limited—it’s typically gated by your character level—so any mutant can wear anything. Every psi-power, Biomutant's take on magic, is open to all characters as well, so there's almost no meaningful difference in your class choice except for how you'll play through the intro. I started off intending to play a psi-power focused character, but the abilities were quickly outpaced by all the powerful weapons I threw together.
Skip the boring sidequests
Or just finish them as you stumble into them. There's a bottomless pile of samey old world technology quests where you need to find five toilets, five telephones, five washing machines—all sorts of junk, and complete the same color matching puzzle on each of them. Mainlining them is a bad, bad idea since they're not much fun and wrapping all five just gifts you a rare crafting component, which you'll find plenty of while chasing your curiosity instead of quest nodes. Save your patience and finish them ambiently.
Resist the desire to loot everything
The stuff is everywhere. Feel free to loot whatever you like in the early hours, but after that I'd hold off and stick to the rare stuff, denoted by a yellow or red glow emitting from the container. I got pretty tired watching the same looting animation only to see some weak shit pop up. My inventory was overflowing. Don't be like me. Sell some of it, break the rest down, then limit yourself to the good stuff.
Prioritize fashion over function
With the JCPenney's worth of loot you accumulate, intentionally or not, you might feel the impulse to min-max. It's OK, gamer. Let go. Biomutant hands out power quickly, so you'll get a ton of powerful weapons and basically all the psi-powers in the game long before you're finished. Live your short animal life right: express yourself. Maybe use the outfits tab to save a min-max outfit just in case, but otherwise, dress up like a JNCO jeans catalogue model. Dress in whatever looks best and forget the rest.
The morality system is simpler than it looks
Biomutant's morality system doesn't bear too much weight on how you're perceived in the world, at least until the very end, and you'll have plenty of time to tip the scales until then. Follow your heart, or just follow whatever psi-powers your alignment unlocks. The dark side's telekinesis is a pretty tough one to resist, honestly.
Don't worry about committing to one side either. If you have a change of heart, the best way for a quick alignment change is through the strangers in distress quests. There are something like 23 caged mutants to free, and after each you'll get the option to let them go or straight up murder them, for some reason. It's a simple avenue for juicing your kindness or cruelty.
Soak it in
I really enjoyed my first lap around Biomutant's world. It's best enjoyed when you ignore the quests and just wander, taking in the lovely vistas and studying the odd creatures (even if they're all reskinned versions of the same archetypes). Make good use of that screenshot tool. We don't get games that look quite as odd and pretty as Biomutant on PC often.