I think that no matter how beautiful your site’s design is and no matter how interesting content it has – personal sites have minimum success. And in virtue of the site is private this is true. It is very difficult to promote your site without knowing special ruses and tricks. Or may be somebody can argue with me?
I'd define a personal site as one you put up specifically to share information with family and friends. As such, I wouldn't see any reason to promote it, except for letting those specific people know about it. No one else would have any use for it, so it wouldn't make sense to monetize it, IMHO, unless you have lots of friends and family.
But are you possibly defining personal sites more broadly than that?
(Not sure if this is the right part of the forum for this question, but I'm sure a mod will move it if necessary.)
The design of a site in general plays an essential part when it comes to user friendliness. This might help you in the rankings and it might also help you get more readers but that is just a possibility. It could turn the other way round. I have noticed that most of the top bloggers use the design change as a way to maintain their already established traffic. You have to bear in mind that all these sites/blogs have great authority among readers. So I'd suggest that you focus on other means of promoting your site such as SEO, bookmarking and blogging