Advice needed - growth by content, links and adwords

Hello,

I'm building an online b2b SaaS portal. I am planning to grow visibility by targeted Google adnetwork campaigns, developing blog content and buying guest posts. Budget is tight for now.

I've read a lot on growing hacks and ended up with these methods and a list of questions, so if you can drop your advice I would highly appreciate it.

1. Guest posts
- what domain age and authority should I consider absolute minimum?
- is Google PR dead or still a valuable measurement?
- for starting, is it worth 1-2 articles with high PR/DA per month or to go with 8-10 guest posts on lower PR/DA sites, in the same budget?

2. Unique content
- what is a fair price for a quality, unique 500-word article on technology topics? I see anything from 3$ to 100$, don't have a clue what is fair.

3. Targeted Google adnetwork seems a better idea for me compared to search keywords, since I'm on a tight budget. Do you see other alternatives to this?

4. Are press releases worth when launching a new product? If so, do you have any recommendations regarding PR brokers or pricing range?

5. Any other ideas?

Thanks guys!