Hi Luke, if you're looking for a 10%-30%-XX% ratio of links I think you won't ever find nothing regarding this.
Even if you'll find that I recommend you to not follow that guide just because: only google knows how much weight they give to each link and also because google can change their algo on a weekly or daily basis, but your seo strategy should be long term based.
So in that sense I strongly recommnend to be just natural. If your site is good you probably see it in blogs, directories, other sites, and also on comments, forums etc etc. Everything is good if it's balanced and natural. Try to avoid any kind of pattern and let things flow up trying to avoid huge unnatural increases.
Also you may consider seeing how your best competitors are doing and try to follow their same strategy.
