Wow, from 0 to 7.. yes very interesting question.. If you have solution, please share it also here so we all benefit from it. Anyone?
I think SERP is more important, but if you want to sell backlinks, then, yeah.. go for PR. Anyway, avoid nofollow, IIRC, Google doesn't even count it.
First, 'No Follow' will not help you much for link building, but might generate traffic from popular blogs. Second, you will not be able to manually get a PR7, you'll need to have a pretty good website that big websites talk about Good luck
I sorta lol'd. In order to get to PR7, you're going to have to do more than just manual link building. And don't spam blogs with irrelevant posts either.
If you are using the same sites to leave your comments, you only want to leave one comment for each page on your site.