The best way to do SEO without paying someone else is to teach yourself how to do the basics. FIrst, you should read several resources about SEO such as: http://moz.com/beginners-guide-to-seo Then, you should use a few free tools such as http://marketing.grader.com/ and http://raventools.com/ (Free for 30 Days) to audit your existing site. Then, implement everything you learned and fix everything the tools say is broken. Keep working at it until you rank #1 or aren't sure what else you have left to do.
Ultimately, you get what you pay for with SEO. You can certainly teach yourself the basics, but if you want to compete in a competitive market then hiring a real expert may be worthwhile once you've done what you can on your own.
