QUOTE: “Some things don’t change — users’ expectations, in particular. The popups of the early 2000s have reincarnated as modal windows, and are hated just as viscerally today as they were over a decade ago. Automatically playing audio is received just as negatively today. The following ad characteristics remained just as annoying for participants as they were in the early 2000s: Pops up – Slow loading time – Covers what you are trying to see – Moves content around – Occupies most of the page – Automatically plays sound.” Therese Fessenden, Nielsen Norman Group 2017
Consider how well you know your industry. If you have been in business for a while and already know what your customers want and how to best reach them, you may want to start to build a long-term SEO strategy that will provide value over time. If you aren’t sure how customers and competitors will respond to your offerings or content, you may want to consider an SEM campaign that allows you to test your ideas, products, and services. Use these sites for market research to better understand your target audience and your position in the industry.
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.