So ive been reading the players companion rules for designing a new spell in preperation for when my mage gets to that point. I currently have 8 con due to getting reincarnated and want to design a spell that boosts con by 1 point preferably permanently, but at least for a couple days so i can gain some hp back. Alternatively i could just create a spell that permanently/over a few days boosts hp directly. The problem I’m having is i cant really find a base effect to start figuring out the cost. Basically my question is how to stat out spells like that.
Permanent stat change is probably ritual-level stuff.
-Your DM
My question is more how to stat it out as both of those things hp and con boosting are not given anywhere in examples
If you want to go easy on yourself, it’s Transmogrification. You’re designing a spell that polymorphs you into a version of yourself with +1 CON.
And then call it Oscar Goldman’s Rehabilitating Ritual.
Ogre power, an Arcane 2 spell, grants the wearer an 18 STR, the ability to deal 1d4 unarmed, and 10 extra stone of carrying for 3 turns. Your effect is probably less pronounced but you’ll be wanting a longer duration.
That being said, your DM just ruled earlier in the thread so… that’s that 
Ok so what about a spell that gives extra hp how would that stat out.
Necromantic potence. 1d10+caster level temp hp.
You aren’t going to be able to stat up a permanent stat boost spell. That’s wish territory.
Based on that, and going straight off the spell guidelines in PC:
Transmogrification: Current form gains strength of an ogre (40)
Range: Self (x0.5)
Duration: Indefinite (permanent until dispelled) (x3.5)
Final cost: 70 (arcane) / 91 (divine)
So “permanent” ogre strength could, by the book, be done as a level 7 arcane ritual, which fits with the GM’s earlier post that this is “probably ritual-level stuff”. Personally, if applied to CON instead of STR, I’d say it’s the same cost, but YGMMV.
Still, that 40 points is for a score of 18, with some extras.
3E D&D and Pathfinder have the various stat boosting spells at 2nd level, and a weaker base effect. For ACKS, call it… 20 points to increase a stat mod by +1, just as a ball-park figure. Day long, self only makes it 30, for a strong 3rd level spell, or if that seems low make it touch range for 36 and a mid-range 4th level spell.
Here’s something I cane up with for another game, but never got to use.
Temper the Flesh
4th level Arcane
range Touch, save negates unless willing
The target touched re-rolls their entire total hit dice, and takes the higher of the new or existing total for their permanent hit points. The target simultaneously ages 1 year for each hit die rolled; no effect short of a wish can mitigate or reverse this effect.
(Aging would be 3/5 for dwarfs/elves in ACKS of course.)
The tricky part is pegging that base effect in ACKS. Looking at the scale, a number of utility abilities come in at 20, gaseous form is 30, incorporeal is 40, ogre strength is 40, giant strength is 80. Bonus hit points… maybe 40? Less flashy than 18 strength or incorporeality, but just as valuable for staying alive when you start taking damage.
So that’d be 40 x0.6 (touch) x0.3 (aging) x1 (saving throw) x3.5 (permanent until dispelled, but I’ll pull something off the Walls list and use:) x1.5 (not affected by dispel magic) equals 37.8. A 4th level spell, if you buy my cost for that base effect.
My old version was written up at 3rd level. At the time I thought that was not terribly broken, but it never did get tested. I’m not unhappy with 4th level now.
There’s still a judgement call about letting that in your campaign, because its easy to see the whole party re-rolling hit points right up to the edge of middle age. I’d be tempted to add in some monsters that aged on a hit in place of energy drain, and just tell my players I was doing so. 
Oooohh… I like that idea. Makes age matter more and the insidious “gotcha” of level drains go away.
I’d be tempted to make any spell that ages, de-ages, or otherwise alters the natural course of time into a lure for such a being (maybe a “chronovore” that is similar to a ghoul, but the claw attacks are normal, and the bite attack ages the target as it eats years of the target’s life?).