It won't be as imaginative as Xanth, but as others have mentioned...use the human for most of them (obviously, if they are a centaur...don't use humans as the race...etc).
I'd then roll on 1d10. On a roll 1-9 that's the level of spell they get. If they roll a 0...they are out of luck...sorry...better luck next time. They get a free feat for their magic ability.
I'd then have them roll a 1d4 to determine which spell list they get their talent from. 1=bard 2=cleric 3=wizard 4=warlock
I'd then number a table with percentages 01-00 and assign a percentage to each spell of each level. They roll on that table to see which spell is their talent. How often they can use it depends on how magical a campaign you are running.
For High magic they can use that spell anytime they wish as their talent.
For lower magic, they can cast it once every long rest.
There probably won't be any balance between characters with this type of creation though...but in Xanth magical talents vary widely between characters anyways.