You want very high Strength because the amount of weight you can carry is directly dependent on your Strength value. Iirc, you can carry two stone of weight per point of strength. Higher Strength -> Hold more stuff. The more stuff you can hold, the less picky you have to be about what you carry around. Your max weight is set once your character is created.
Higher Vitality translates to higher hp, but you can heal lost hp, and your max hp increases as you level up.
Higher Intelligence probably increases your max mana, but max mana is rarely an issue as you raise your Mana skill. There are plenty of ways to regen mana.
I don't even know what Dexterity does, if anything. Across many runs, I've never noticed any issue regardless of whether it was high or low.
You have enough mantra points to max out about 6 skills, with maybe a little left over. Therefore the advice I would give is to spend your limited number of mantras on maxing Attack, Defense, and a weapon skill of your choice (that isn't Missile) as the most important choices. Mana and Casting are both needed if you want to cast spells. Lore is a very useful skill throughout the game.
Skill descriptions:
Attack: Increases the chance that a particular swing will deal damage to an enemy (assuming the enemy is in range).
Defense: Reduces the chance that an enemy swing will deal damage to you.
Weapon skill: Increases the chance that a particular swing will deal damage to an enemy, reduces the chance an enemy swing will deal damage to you, and reduces the chance that a given swing by you will cause the weapon itself to become more damaged. With a high weapon skill, you can reliably bash doors with your weapon without your weapon being damaged in the process. With low weapon skill, you can literally break your weapon trying to hit some of the tougher monsters (like the Gazer in the mines on level 2).
Your fists aren't subject to weapon damage, so you can always bash down a door with your fist (if the door is bashable) without any risk to your weapon.
Don't use choose missile weapons because you can't fire a missile weapon when a monster is right in your face. Monsters are either trying to get in that range, or else YOU want to get in that range because they have dangerous ranged attacks (ex. Fire Elementals and Gazers), so don't pick Missile. If you want to use a ranged attack, there are several wands with a lot of Magic Arrow charges, as well as scrolls and wands of various other attack spells. Also, ammo is an issue for missile weapons, as noted earlier in this thread.
Every weapon skill (except Missile) is perfectly feasible for a full run; you find an early example of each class (dagger/short sword, hand axe, cudgel) in the first rooms you can explore. You never need to use a weapon outside your chosen weapon type.
Mana: More points in this directly increases the amount of mana you have available.
Casting: More points in this allows you to cast higher circle spells, and it reduces the chance that a given casting attempt will fail or backfire (backfires deal a little damage to you). Some spells, like Magic Arrow, can be cast with very little casting skill. Some spells, like Tremor, require a lot more casting skill.
Lore: Increases the chance that you can identify what effect a magical item has, or even whether it is magical at all. The first time you right click on an item, the RNG determines whether you identify the item as magical and whether you identify the specific magic of the item. High Lore increases the success chance of each of these occurances. If you don't have any points in Lore, then you'll have to be very lucky to determine whether that sword you just found is magical. High Lore gives you a decent chance to identify whether that red potion restores life, restores mana, causes hallucinations, or poisons you. The Name Enchantment spell, the wand of Name Enchantment, and the mage guy that charges to id items all have a 100% success rate.
Swimming: Lets you be swimming in the water longer before you start taking drowning damage. You mostly don't have to swim, so this skill isn't useful. You can use the arrows on the compass to advances by whole tiles, so this skill is completely unneeded; you can skip ahead fast enough that you'll only take drowning damage if you are trying to drown.
Appraise: this is an assumption on my part based on the in-game text provided alongside the mantra. This skill increases your success rate in identifying the quality of a deal when you are trading items with an NPC. What isn't an assumption on my part: You can afford to take a terrible deal every time by simply trading large stacks of free fish for whatever it is you want. This skill is therefore useless.
Charm: this is an assumption on my part based on the in-game text provided alongside the mantra. This skill increases the chance that an NPC will accept a deal that isn't favorable to them in terms of item value. What isn't an assumption on my part: You can afford to take a terrible deal every time by simply trading large stacks of free fish for whatever it is you want. This skill is therefore useless. This skill does not affect conversation trees to progress through the game.
Search: I think this skill is supposed to help you locate secret doors. You can find all the secret doors just fine without any points in the skill. Therefore this skill is useless.
Track: I'm assuming this helps identify what monsters are nearby when you use the F9 (or whichever key it is) that tries to locate nearby monsters. Instead of using that key, you could just go look. This skill is useless.
Sneak: I'm assuming this helps you move around monsters without being detected. It might not work if you have a light (since a light in the dark is a beacon), so unless you want to sneak in the dark, this skill is useless. You never need to sneak by anything, and light is too convenient.
Traps: I'm assuming this increases the chance of successfully spotting and removing traps on treasure. There are so few traps that finding one is noteworthy, and none of them are on treasure you need, so this skill is useless.
Lockpick: Increases the chance of successfully picking a lock. This skill can be useful, but not every lock can be picked.
Repair: Allows you to repair (most of) your weapons and armor yourself. You can't repair jeweled gear, but you can repair Badly Worn gear. Shak can repair jeweled gear, he won't repair Badly Worn gear, and he is still needed for the special repair job.
Acrobat: Reduces the amount of damage you take when you fall from heights or slam into walls. However, it only reduces wall damage if you hit the wall straight on; personal experience shows it doesn't help if you hit the wall at an angle. A few points can be useful, but you don't ever have to fall from great heights and you can heal damage, so you don't need many (or any) points here.