With regard to magegift, I'd suggest use of the 5/90/5 rule.
This would have 5% of the population as 'naturals', who would be doing small-scale manipulations as part of their day-to-day life anyway - they might be 'lucky', they might have a talent area like painting - magegift is no substitute for training and hard practice in an area, just gives a bit of natural 'flare'. Note that "anti-mages", those with a talent for suppressing magic around them, are normally 'naturals'.
90% of the population are 'normals', they can train to use magic but it is a hard grind, and they need plenty of motivation to stick to it. Most normals only develop in one magical area, if at all, and they tend to rely on hard-trained skill and experience, rather than raw talent. Occasionally trauma might cause a particular magic area to develop, to quite an amazing degree, but this is 'distorted', and 'fragile'.
5% of the population are 'duds', and can (with difficulty) train to use magical items which provide the magical power, but are very unlikely to ever do more than one or two simple bits of magic themselves. Almost all of these have a compensating talent in some non-magical area.
One advantage of 'duds' over 'normals' is they don't show up quite so easily to magic-based senses, and magical defences tend to work better for them, as they don't have any magical talent which "sticks out" beyond the defences, and provides an avenue for attack. Magical tricks which depend on using the target's own magical power against them fail on duds, and some creatures of magic without physical senses just can't sense duds.
Edit: If you want to bias this for the population of the Wizards, you could increase the proportion of the 'naturals', to 10%, or even 15% (I wouldn't recommend any higher) - I've leave the proportion of 'duds' at 5%.
META: This doesn't directly affect any of the characters in stories written - they have the required magegift for the story. But, it gives background information about (potential) magical talent in the society in which you might set the story.
Just some suggestions...
--
"It is the business of the future to be dangerous" - Hawkwind
This would have 5% of the population as 'naturals', who would be doing small-scale manipulations as part of their day-to-day life anyway - they might be 'lucky', they might have a talent area like painting - magegift is no substitute for training and hard practice in an area, just gives a bit of natural 'flare'. Note that "anti-mages", those with a talent for suppressing magic around them, are normally 'naturals'.
90% of the population are 'normals', they can train to use magic but it is a hard grind, and they need plenty of motivation to stick to it. Most normals only develop in one magical area, if at all, and they tend to rely on hard-trained skill and experience, rather than raw talent. Occasionally trauma might cause a particular magic area to develop, to quite an amazing degree, but this is 'distorted', and 'fragile'.
5% of the population are 'duds', and can (with difficulty) train to use magical items which provide the magical power, but are very unlikely to ever do more than one or two simple bits of magic themselves. Almost all of these have a compensating talent in some non-magical area.
One advantage of 'duds' over 'normals' is they don't show up quite so easily to magic-based senses, and magical defences tend to work better for them, as they don't have any magical talent which "sticks out" beyond the defences, and provides an avenue for attack. Magical tricks which depend on using the target's own magical power against them fail on duds, and some creatures of magic without physical senses just can't sense duds.
Edit: If you want to bias this for the population of the Wizards, you could increase the proportion of the 'naturals', to 10%, or even 15% (I wouldn't recommend any higher) - I've leave the proportion of 'duds' at 5%.
META: This doesn't directly affect any of the characters in stories written - they have the required magegift for the story. But, it gives background information about (potential) magical talent in the society in which you might set the story.
Just some suggestions...
--
"It is the business of the future to be dangerous" - Hawkwind