Consider the current status of your website. When you create a marketing strategy, look for the “low-hanging fruit”, or the opportunities that will make the biggest impact with the least amount of work Click & Tweet! . So before you launch a search marketing campaign, research your website to see where you may have the potential to grow an organic SEO strategy that is already working before putting money into an SEM campaign.
Ask for a technical and search audit for your site to learn what they think needs to be done, why, and what the expected outcome should be. You'll probably have to pay for this. You will probably have to give them read-only access to your site on Search Console. (At this stage, don't grant them write access.) Your prospective SEO should be able to give you realistic estimates of improvement, and an estimate of the work involved. If they guarantee you that their changes will give you first place in search results, find someone else.