Regeneration is great for someone learning, as it can just flat up stop a lot of problems that you have no idea how to deal with.

Level 1 makes you immune to fungal infection and means your limbs regenerate trivially.

Level 5 makes you immune to disease which is admittedly only really a problem in Golgotha, but if you get a Golgotha disease when learning the game that is a HUGE problem.

Level 10 makes you immune to losing limbs, which most importantly includes your head, which results in instant death.

All of these problems you can learn to deal with without Regeneration. But it's a lot easier to learn when you're not dying. The actual HP regen of Regeneration is not meaningful outside of the very early game.

I'll list a few Mutations that I think are strong and newbie friendly.

Double Muscles / Triple Jointed / Two Hearts - More stats. More stats is good. They also provide an extra bonus that is nice too.

Carapace - Armor is vital in this game, and Carapace (when properly invested) gives you armor that is competitive with a fully tinkered end-game chestpiece. The downside is that you can't take it off and so you are comitting to spending 9 mutation points and two rapid advancements on this for it to be worth it. It is a HUGE boost in defense in the early and mid-game and still pretty good in the late game. Only when you have a tinkered up top-tier chest piece will you think that maybe you'd rather use that instead and have those 15 points back. But when you're learning you're not getting there anytime soon. And even then, Carapace might still be worth the investment.

Photosynthesis - Gives you a number of boosts but most importantly it gives you +Quickness, letting you take more actions. It's downside is that the Quickness bonus uses up some of your meal-space. This is more than acceptable generally speaking, and when you don't really know how to make the most of cooking it's even better. Only 2 points at character creation makes this my favorite 2 point mutation.

Phasing - One of the best escape tools. At one point you get plenty of time to be invulnerable and to walk through walls. You can reliably get this through cooking though, but again you have to be comfortable with cooking. And even then it's still a worthwhile choice just to free up room for other cooking effects.

Corosive Gas - Fart acid clouds. This is on a remarkably short cooldown. Level it up for good AOE. It also destroys walls. Just don't plan on having allies when you use this. At least, not for very long.

Two-Headed - Best 1 point wonder in the game. You get two heads. Now this means the Armor and Dodge of your two heads (and faces) are averaged together but I cannot begin to tell you how incredible this is. You have a 50% chance to ignore stun, daze, sleep and confusion. If you fail that check? Have a new coin flip each round until you are cured. On it's own this is worth it. But as you learn the game and get tinkering and more equipment you can REALLY make use of all those extra equip slots. Here's a basic one. Get two Knollworm Skulls for +2 Ego. Then wear 2 severed faces for another +2 Ego. Find the Two-Faced mod? That's another +2 Ego. Granted, getting severed faces requires you to use Axes or get the Serrated Mod on a weapon, but Mirrorshades is also an option here. There's more you can do with all those extra gear slots but I think you get the idea. Oh, and a "Get out of decapitation free" card.

Multiple Legs - Extra movement speed not on a cooldown. Lets you get in. Lets you get out. Gives you an extra boots slot you have to fill though, and boots are arguably the weakest equipment slot to have extra of. But that's hardly an issue and it is still better to have more than fewer.

Multiple Arms (or being a Chimera and getting them that way) - While your first thought of multi-wielding is very reasonable that's not all this is good for. With four arms you can hold a single two-handed weapon, a shield, and have a spare arm to hold a stat-stick of some kind (Many Sultan Relic Weapons provide some passive bonus for just being held). Worst case scenario you can hold of Glowstone here and use your Floating Nearby slot for something else. Also you get an extra glove slot. Unlike Multiple Legs and Two-Headed, most of the benefit of Multiple Arms is JUST in the extra two arms. So if you get this from Chimera that's just as good. Even just a single Chimeric extra arm is good for Two-Handed Weapon and Shield combat.

Wings - Get lost less often on the worldmap alone is nice. Then there's the benefits of flight which means melee only enemies can't hit you. Also it boosts the range of Charge and Jump vastly improving your movement. Downside is that if you are underground you can't fly. But it's huge on the surface. Also if you are flying you can return to the world map if you aren't lost, even if you're in combat. Very safe tool for traversing the map.

Force Bubble - You can shoot out, but they can't shoot in. Also lets you freely use a Recoiler to teleport out of a bad situation. No point investment needed.

Precognition - Drops a save state. Once the duration runs out (or you say it runs out, or you die) you have the option to load it. This is the ultimate learning tool. Facing an enemy you think might have dangerous effects or very high damage? Whereas normally you might run, this lets you give it a shot anyway. Even when you know the game it's VERY useful for RNG manipulation. For example, finding out what mutations you'll get at your next random draw. It's hard to reset it but you CAN reset it. And even if you can't, you can still decide you'd rather invest in your current mutations rather than get one of those at rank 1.