This is a discussion we will need to have to see what works best for your business in your targeted area.
SEO is important to rank organically on search engines whereas SEM allows you to pay for the top ranking positions. If your businesses market is heavily diluted (typically for plumbers, dentists, physiotherapists) then you may benefit from paying to be at the top of search results. Whereas for less common businesses (think bicycle tyre repairs, lawn mower mechanics, organic herbal stores) it can be easier to appear at the top of search results organically (through SEO) and therefore SEM may not be necessary.
Google your business in your area and see how many pop up – this will give you an idea of what your digital marketing needs are!