Hello Cache, you shouldn't concentrate so much on the PageRank issue so much. If i where you i would concentrate more on doing work to improve your SERP's and put your time in learning SEO since this will help increase the traffic to your website(s).
Pagerank isn't that important factor to have traffic for your website, there are people that have low pagerank but have more traffic then someone with a higher pagerank.
So learn more about Off-Page SEO such a backlink building, link baiting and On-Page/Site such as relevant Page titles and so on.
This will create more traffic.
It's hard to say what route you should take if you want to buy more domains or develop but i have to say that all depends on your financial situation and the kind/quality and amount of domains in your portfolio.
Make a list of the top 10 domains in your portfolio that you think has the best potential to generate traffic/revenue based on the concept/idea that can be used for the domain.
Then review that list again and choose your top 5 then do a second review and estimate which of these five can you develop for the cheapest price going up to the most expensive price. You would have to plan what features you would like to have on your site(s) plus look around who can do this for you against what prices.
Example:
Domain1: $500
Domain2: $400
Domain3: $300
Domain4: $200
Domain5: $100
When you are at this point i would start with Domain5 if my budget would only allow me to develop Domain5. If i would have a better budget i would take in mind wich project would create better revenue and choose to develop that domain, this way i can develop the other domains much faster.
If Domain5 is starting to generate some revenue i would use that revenue to develop Domain4 for $200 and use some of this revenue to buy some new domains if i would see domains available to my liking. This all depends how much revenue you would make with Domain5.
This would mean you would first have to have a little budget to develop the first project and with good effort learning SEO to increase your traffic, revenue increase will hopefully follow.
This all depends on the domains you have and the ideas you have in mind and only you can tell what potential they have.
But this would be mine approach.
-Learn SEO and keep learning since SEO is dynamic and is not based on a set formula and factors.
-Then try to obtain a small budget to develop a domain as a first start by means to your disposal and is within your capacity. You would have to take this in mind as well when filtering out the domains you wish to develop and what kind of budget is needed to develop.
(Of course you don't have to know the ins and outs of SEO first and only then to continue to step two but do what you have to do to get your budget available and do your SEO study in between)
If all goes well and you have generated some revenue then develop your second domain/idea/project. Once again of all the domains in your list estimate which of the domains could produce the most revenue and which of those you can afford to develop.
Repeat the process again to a point so that you have a small network of sites that you can maintain.
Don't overstretch yourself or the quality of the site/experience depending on the concept of the site will degrade and will cause your growth to decrease.
Once again only you can tell when and how this will be the case.
Development is important to continue your domaining addiction
those registration fees will return each year
And if your developed domains bring in some revenue to cover the reg fees for your domain portfolio plus a little extra on the side then you have a nice thing going for yourself.
Plus your if your undeveloped parked domains bring in some revenue that's only a bonus
