SEO is very time consuming that is why good SEO companies charge a lot per month. If you are willing to save money and put time into SEO you have two options:
1- Do it Yourself - A lot of material available online
2- Get SEO consulting services - These are individuals or companies that will analyze your site and keywords and provide you with a detailed report on what is missing to rank better but the bulk of the work is done by you.

I recommend number 2 and I might be biased because I offer SEO consulting services but that is an affordable and faster way to get on the right track.