I also run two coupon websites and one of them is earning me money. I don't use WordPress as it is very difficult to run and optimize WordPress websites for coupons. Hired one guy on Upwork and wasted 400 USD. Later I developed my own cms for coupon management using strapi . You can also use contentful for coupon CMS. It works great.
To develop a site like OP mentioned you need a crawler that can crawl your target websites, scrap data, and push that data into your backend cms like contentful or strapi. Bit technical I would say. Using WordPress is not a good solution for coupon websites if you are not a WordPress developer yourself