PageRank does not go up in equal steps, for instance PR2 is double a PR1, PR3 Is double a PR2 and so on, so going up from a PageRank of 1 to 2 isn't hard, but going from a PageRank 5 to 6 is a huge task (as the below bar chart shows)
To give you an idea of general PageRank here is a small list of sites and their PR
Google and Facebook PR10
Youtube and Twitter PR9
Asos and Ebay.co.uk PR6
"How Do I Get PageRank?"
PageRank is a purely mathematical equation and you get it from something called "Link Juice" which is passed through links. If another site links to blog and it's a PR4, some of their PageRank will be passed on to you.. so basically, the more links to your blog from high PageRank sites the better.
"What Will A Higher PageRank Do For me?"
1. If you fully optimize your blog for a Keyword by putting it in your Blog Title, then having links from relevant sites with high PR will help your blog rank better in search engines, meaning your blog will be more easily findable to searchers.
2. It makes your blog more attractive to advertisers.