If this is a website that you want to profit from in the long run then I'd recommend you take things relatively slow - yes create web 2.0 pages and a PBN is always a good idea in my opinion - just don't build too many links too quickly to begin with. You'll be better off by steadily increasing the amount of backlinks to your site as the number of pages on your site grows and don't forget that deep links to inner pages are an important form of diversification too (then funnelling the juice back to your homepage or other most important pages through internal links).
For added diversity, you might:
- record a podcast and submit it to a few of the major pocast sites
- write an article and turn it into a pdf and submit to document sharing sites
- create a multi-page presentation and submit to presentation sites
These are some of the easiest ways to get a variety of backlinks pointing at your site, but obviously there are more that require more work such as infographics, videos, targeted guest blogging, broken link building, etc. I tend to avoid forum links and blog comments but these are also an option - just focus on quality over quantity if you're going to do them.