Also lets not forget that
PR has no correlation to overall traffic. Remember that ultimately it is the amount of traffic that is going to make or break a site. Back links and
PR will help with getting ad dollars though as they increase your visibility and advertisers like this as well, but they do look at your traffic stats and many will not advertise on a site with a high pagerank and no measurable traffic. So your plan has to well balanced.
Natural backlinks with proper anchor text though will get your page rank up as you get your links on more sites with varying
PR's which in turn will eventually result in higher rankings in the Search engine result pages. Really a vicious circle. Or you could do as some sites do at the beginning and pay for your traffic if you have the money to do this and eventually if your site becomes popular they will link to your site and your
PR will shoot up from this as well. Since most people do not have the money needed to do this at the begining doing the hard work of getting natural links is the only way they can truely accomplish all three.
If you are, however, trying to get your
PR up this could happen quickly with your first update if you have a good mix of higher
PR sites linking back to you. Or you may have to go through a few cycles to hit the up levels of
PR. It all depends on your willingness to work at it and your budget if you plan on paying for one-way links.
Personally I would worry more about my traffic and back-links from as many relevant sites as I could.
PR is a third place for me on this list.