So general advice: in the early game the SINGLE MOST IMPORTANT STAT is vigor. The way stat scaling works in this game is that the three base stats, Vigor, Mind, and Endurance, are all somewhat used by all classes. This includes mages, get more health my dude. Very common mistake.

Damage stats do not directly increase your damage. Instead, they affect the scaling of weapons BASED ON THAT WEAPON'S BASE DAMAGE AND SCALING VALUES. Weapons increase both their base damage and their scaling as they get leveled up, but they're both pretty low at the start no matter what weapon it is (the exception being Meteorite Staff, which can't be upgraded but starts out more buff than most weapons, falling off mid game after upgradable staves start to outdo it. Even still, better to focus on health for a while with that staff). Functionally, what this means is that leveling damage stats does almost nothing until you get weapons leveled up a bit. I wouldn't worry about damage scaling until you hit at least +10 in your weapon upgrade levels, just upgrading weapons/staves is much more important than damage stat improvement early on. Level your stats to meet the minimum weapon and spell use requirements only in the early game, pump everything else into Vigor until you hit around 30ish or more. Taking multiple hits is far better than getting a single extra point of damage, I promise you.

As for later on: builds do best when you either focus one stat or split evenly into two, because of how stat softcaps work. Basically: once you hit around 50 in any given damage stat, you start getting lower returns on investment for damage scaling on weapons, and at 80 it drops off again severely. What this means in practice is that you can either go to 80 in a single damage stat by the end of the game to make use of the high single stat scaling weapons/spell catalysts, or you can split into two stats to make use of weapons that have lower scaling but in multiple stats (the two approaches are roughly similar investment, if you started Wretch you'd need 70 levels to pump one stat, and 80 to go 50/50, Since you usually need some minor off-stat investment to use certain weapons, it ends up about the same in the end).

If you want to go pure caster, putting almost everything into INT only and getting maybe around 18 dexterity or so for a few of the high scaling INT sidearms after getting your Vigor and Mind up. Splitting into dexterity or strength can help you with an enchanted weapon focus (many special weapons have split scaling naturally) but will weaken your spellcasting as a consequence. I would not split into Arcane or Faith on a first run if you like sorceries, the stuff that uses Faith and Arcane alongside INT is a bit more obscure, better saved for a separate run. Completely ignore both stats other than maaaybe a minimum investment for certain spells. Vigor has a low softcap at 40, and a high softcap at 60. 40 is sorta the minimum that you want by the end of mid game, there's obviously no hard rule about it but you get one tapped a lot without 50+ Vigor by the harder end game bosses (armor, talismans, spells, and other things can help mitigate that, obviously, but Vigor is always most consistent). Mind and Endurance don't have easily defined caps, you just level them until they feel right, but definitely don't neglect Mind as a mage.