I generally go with the following:
MLB 15%
MiLB. 20%
Amateur 30%
International 35%
I favour International a bit because to me it's such a crap shoot to find good players there. I don't use the IAFA system though, just Scouting Discoveries turned up to "A lot (16 per year)".
Of course Amateur is a no brainer to me - scout, scout, scout and then it's still a crap shoot.
Majors and minors I can get a good feel by stats usually, so less spent there.
I'm with Pelican - would be nice to know how this allocation affects reports and their accuracy. Though I'm thinking accuracy would be determined by frequency.