Page Rank is not a major feature of the success of a web site. Much more important is good, valuable and relevant (i.e. relevant to the subject of the web site, not just any old junk). Inbound links are good but again only if they come from sites that deal with a similar subject. Buying links is never a good idea nor is buying a PR5-6 site just to give another link to your main site. If you don't keep the site you buy fresh with new content on a regular basis it will soon lose PR anyway but, more importantly, will fall from the first pages of the search engine in quick time.
So, the summary of all that is, have a good product, fill your web site with really good content, persuade other web masters to link to your site (more valuable if it is a one-way link to you, not reciprocal) and be patient. High traffic does not happen overnight! You have to build a reputation.
The other area for attention is raising your internet profile in general. So, write interesting articles and submit them to article directories with your web address in your sig. Join forums relating to your subject matter and participate (and again add your sig, if it is allowed). And any press attention you can get is very valuable. If you have anything interesting happening with your business do press releases to trade journals, local press, national press etc.