First of all check your On page SEO and than go for off page SEO. Because if your On page SEO is not good then will not crawl your site very well. In off page SEO try to submit your link in high page rank sites.
It's not so easy to getting top position on google, by the way you have to optimize your website and submit your site map with google first then do some social book marking will help for indexing quickly.
I haven't done much to my site, yet the Page Rank is now 4 and the Alexa Rank is 278,799. How can i rank higher for the keyword fiverr or freelance? I don't understand SEO, which everybody keeps telling me about. I don't have a high budget, what can i do?
Well after following the above important corrections you must have to wait until Google update their ranking and please be careful on using duplicate contents.
There are several reasons why your site won't show up or won't show up as high as you expected, the keyword could be competitive, your site is relatively new, there are not enough authority backlinks to justify it being shown for that keyword, it has been penalised e.t.c