No need to pay SEO agencies big money to optimise your website or keep searching the internet on how to do Search Engine Optimization (SEO) yourself. Google has now published its own SEO documentation which you can now Do It Yourself (DIY). What a better way to get a SEO documentation from Google instead of paying big bucks to SEO agencies where most of them give you the same kind of information/guidelines that are already widely available out on Google itself. I guess the money paid to agencies is at least they can project manage it for you and make sure that you are doing the right thing and you don't have to worry. This is the same as paying migration consultants where most if not all migration information is on the internet or the immigration government site but yet you want to have the peace of mind paying the expert to do the right thing for you so you don't have to worry about it. You can download Google's search engine optimization starter guide
here from https://support.google.com/webmasters/answer/35291. or directly from www.google.com/webmasters/docs/search-engine-optimization-starter-guide.pdf.