So I have a website that you can buy and sell domains at its www.grabthe.com Any help would be awesome! Thanks
You can promote your site on social media sites start with facebook. Join groups with relevant interest & topic and do postings in them. Also create facebook page & get followers for it by running campaigns on it regularly. Classified ads submission can be one more option for your site type.
Many different ways to do proper SEO best method is quality backlinks but many people don't know how to make quality links here is guide How to build quality backlinks http://www.online3c.com/high-quality-backlinks-2017/
Focus over the On-page optimization and keep the back-linking strategy consistent. Don't give too much backlinks to your site just for ranking purpose.