Hi there. Good for you for getting your SEO campaign off the ground!
You need to be careful when choosing an SEO consultant. There are so many out there claiming to be specialists in this area, who simply don't know what they're doing, and I have fallen victim to this myself in the past!
For me, the best metric is to ask them to show you the analytics for a site they have worked on (ideally one similar to yours). If the key metrics have increased, then you're probably on to something. Then ask them how much time they spent on optimising the site (if it took them 100 hours a month, they are probably going to be too expensive). You'll then be able to make an informed choice.