Adding SEO to a new site

I’ve just finished a site (apart from some minor tweaks still to be done), and would now like to optimise the search process. What are the best plug ins to make this happen ? Is it a straight forward process ?

It’s a gift shop site https://www.lovelythings.org.uk and obviously I would like it so if someone is googling a particular item (e.g. leather chesterfield sofa) my site comes out. Is this possible without throwing ￡￡￡’s at it ?