The problem there is that is that it's absolute rather than relative, so we're looking at actual values of GP spent rather than actual amount spent versus maximum amount that can be spent.
That's the main sticking point of including Skills: if you calculate for GP spent, there's difference between races and it's not entirely certain how many masteries are counted as "maximum".
One possible way of doing it is to look at how far someone chooses to progress their Skills. Using myself as an example again:
I think I've got Eleven skill slots: Two customs from being Prestige, two from the Prestige itself, and seven basics from Shinigami.
Discounting Royal, that's 6 skill ranks per skill, which means a total of 66 ranks.
I've bought 36 of those ranks, opting to completely ignore my Prestige secondary, and both Kidō schools available to me.
That's roughly 55%. If you use 150 as max in one stat, then you can calculate where I am in each specific stat, just as where I am if 400 is max Reiatsu.
Kenshou, since you seem to have Excel open already, will you do the honors?