I think this is not a good idea to have a couple of high-profile people for your 2 sided marketplaces advertisement. Because celebrities generally have less availability and are greater high-priced, with a purpose to have an effect on the level of service that you provide your customers. I think you have to think about the marketing strategy. You should understand how to attract both buyers and sellers.

The good idea is, you have to choose the right professionals, it will save you a lot of time and money. Expert SEO and SMM professionals will promote your website effectively. Another way of growing marketplace popularity is a high-quality website, that is, the fast work and interesting design and, of course, it is the absence of gross bugs including.
I've successfully helped over 150 entrepreneurs, startups, and businesses to create and run marketplaces, and I would be happy to help you. Please send me more information before scheduling a call - so I can give you maximum value for your money. Take a look at the great reviews I’ve received: https://clarity.fm/ripul.chhabra