Its not a good idea to be working out of blogspot, unless you own the domain. Even still, not a good idea because you dont have total control over the site.

First of all if you wanna have a good PR or wanna start off with SEO, try to get a domain... then get out of blogspot... wordpress is a good recommendation =) self hosted wordpress is even better. =)

Increasing PR isn't that important in my opinion. Obviously it is nice to do, but Google only updates their page rank a couple of times a year. If you just focus on the fundamentals like getting high quality backlinks back to your site from other high PR pages, your own PR will take care of itself.

Link exchanging through blog posts will help to increase backlinks and also popularity of your blog.