The stat system isn't going to be using a leveling system, stats will increase based on actions preformed. stats will make it exponentially harder to do something outside of reasonable range, for example, someone with 10 strength isn't going to be able to carry a rock golem no matter what they do, as the strength required would in the 40's for any decent amount of maneuverability.
Most races will have caps to most or all of their stats, so a Lunarik for example will not be able to go past 15 with strength or stamina, but have absolutely no cap on intelligence or wisdom (although their utter lack of magic makes this less useful.). Their willpower caps at 10 (making the majority extremely submissive with anything not directly related to their instincts.) but their dexterity and agility cap at 33 and 41 respectively (meaning ones that trained at it can easily climb a castle wall in about twenty seconds with no equipment whatsoever.) Their charisma caps at about 24, however their clothing choices (completely nude or seizure inducing incandescent rainbowtastic blehness) would give penalties to charisma not interacting with them.
Stats can be increased up to their cap with practice or doing things that would increase them, for example lifting weights daily for several weeks would increase strength and maybe stamina by a point, but you would need to maintain it, laying around and doing nothing would result in losing strength and stamina points for example. Stats are in flux based on activities. The soldier that practices swordsmanship every day would have an increased strength and stamina. The mage that upkeeps the memorization of a spell daily will have increased intelligence and willpower (as forcing yourself to focus on something for a long time every day requires willpower.)
I'll have the whole ruleset done either tomorrow or the day after. It'll make more sense then.
Skills are things that need upkeep, a spell counts as a skill, a school of magic also counts as a skill. You will have a hard time casting a spell from a school of magic you don't know well. You will also have a hard time casting a spell that you never commited to memory or did at one point but haven't upkept it at all.
Races with perfect memory (*cough* Lunarik and Gnomes*cough*) do not have this problem. However most races with perfect memory lack magical ability or have a difficult time learning new things in the first place (Elves).
Skills are something that you build over time, mining or practicing sword fighting would give you skill in those, however they would also count as an upkeep for strength and stamina, also endurance.
It'll be clearer when I post the ruleset.