Traffic from Google is always up and down, like a wave curve. Google does not index all websites at the same time. I have noticed traffic goes up right after they crawl the site. Then it goes down to some extent. I am not expert on this, somebody expert may be able to explain better.
It would be almost impossible to get into the top 20 for myspace layouts. Your best bet is try to get in with more unique keywords, and long tail keywords. You could use this keyword research tool to find the lower searched terms and check them out.. Probably have low competitions. and work on getting combined traffic from those kw layout myspace: Search estimated volume 6,570,260 a month. The sites on the 1st pages for that must be making a killing..