Actually sir SEO can be done by your own if you have the provison to change the content of your own website. Actually i learned SEO by myself from youtube and i think you shouldnt be wasting money on a simple thing like SEO. The only thing you will have a bit confusion is about the advertising if you are not interested in it. The SEO can be learned by yourself
SEO is much more than gaming Google these days, so I'd definitely recommend at least hiring a professional to get you started and on the right path - perhaps just for an initial six month engagement. (Improving the rank of your site organically is a long term 6-12 month process usually) If you need an instant boost, consider Google Adwords / Facebook Marketing which also have benefits when it comes to defining your audience and contributing to long term SEO goals.
If you do decide to look at the SEO of your site by yourself, you will need to:
Learn how to research what keywords / phrases that people are using to search for the product or service that you provide.
Learn how best to create great content that matches the most popular search terms (and niche search terms if you think there is an opportunity). Then be in a position to create content that is both compelling to humans while also meeting Google's requirements to rank well.
You'll need to get familiar with Google Analytics in order to be able to track the success of your content over time and make adjustments frequently. It also helps to understand the Google Adwords platform as a great deal of insight can be gained from creating optimised ads that then give you valuable information to use in long term SEO.
Just my two cents... I'd hire a pro if you want to get real momentum and traffic to your site.
I'd also add, being as active as possible on various social media channels, so you have more chance of your content being shared.
SEO isn't rocket science (well, so long as your site is built well, so that's at least some computer science), but it can be very time consuming, and that's what the effective and honest SEO professionals get paid for, their time directed in the right places.