In short, use int if you want to break the game with massive damage, dex if you want fast weapons with good DPS and nice access to healing, and strength's generally worse but the added poise from most of those weapons keeps you from getting knocked down.
You can build for strength, dexterity, or intelligence. Not really luck, weapons that say they scale with it don't. Luck gives minorly bigger damage boosts than the other damage stats but don't help you unlock the conditions to start using other weapons, and luck doesn't help most magic except for the Dark Cauldron that uses luck to pick between normal attack, health drop, magic drop, or large damage explosion.
The most comfortable build in the game is 6 agility and 20 intelligence. You spend 1 point in agility to unlock using the Weathered Sword or Fine Crested Sword, and in the case of the latter weapon you also need 12 intelligence.
The Weathered Sword becomes the Called Sacred Sword if enhanced with the twinkling ascension path, and gains sacred art damage without any change in stat requirements to use while additionally scaling with int. It's mostly identical to the Crusader's Sword you find much later but with much less stamina consumption, so the extra cost of using a rare upgrade material is worthwhile.
If you don't want to spend a rare twinkling slab and are okay with adding more cost to your minimum stat requirements in exchange for a better weapon, go with the Fine Crested Sword. Its best upgrade path is the normal route so a normal slab you can farm off Minotaurs is all you'll spend at the end. Along with sacred art is also has lightning art damage, which helps it synergize with the Lightning Blade spell to effectively bomb enemies in a large area for big damage with little more than a bit of time striking the lightning rod along with enemies before it sets off.
The Lightning Blade spell (requires 20 int) is the most overpowered in the game because not only is it a large pulsing AoE attack but it chains with itself, which means you can repeatedly cast it to relentlessly pile damage and staggering onto a large area. A simpler spell is the Sword of Praise (requires 13 int), which outcompetes your weapon or the blunderbuss for high damage quickly in close range.
Sacred Art is the best damage type by endgame because your most formidable enemies are demons, including the Final Boss' 2nd phase. The next best is lightning for being able to abuse a powerful spell. Fire and darkness don't seem great late but the spiders in Ragdum's depths are weak to fire. Humanoids are probably weak to darkness but you'll stop caring about those pretty soon.
If int doesn't motivate you, try dex. Sure you'll find joy in a rapier or a katana but the real hidden gem in the dex collection is the Cross Yari (requires 10 str and 15 dex). The stat requirements are steep and it doesn't scale with int but you do get a good moveset with potent staggering, reach, and damage output. It has a tiny bit of fire art in it which unlocks a passive damage multiplier up for fire spells. Its best moveset path is on the standard route so only normal shards, chunks, and slabs are used for its best result. But most importantly the passive healing on this weapon combined with its positive attributes makes it the most effective weapon to heal lost health during the revenge period, because even if it doesn't heal the most health per hit it'll dish out more hits with good damage with enough speed, reach, and staggering to make it more successful than heavier weapons that are more vulnerable and less successful in healing. And additional gimmick to its moveset is a high strike in the middle of its combo, which lets you attack airborne foes or foes standing on platforms above you without jumping.
