For example, at the beginning of Clarity, would it have been better to have a couple "celebrity" experts (Mark Cuban) or 10 non-celebrity experts.
There is no absolute correct answer, as both options have their pros and cons. At the end of the day, you need to bring in as many users, on both sides (experts and people using their services) in order to create traction and gain revenues.
So, if the "Celebrities" are willing to endorse and advertise your platform, then it is better focusing on them, but in most cases, they won't do so, therefore, it would probably be better, and easier, focusing on getting regular (but quality) experts. Also, take into account that "celebrities" usually have less availability and are more expensive, which will affect the level of service that you offer your users.
I've successfully helped over 350 entrepreneurs, startups and businesses, and I would be happy to help you. After scheduling a call, please send me some background information so that I can prepare in advance - thus giving you maximum value for your money. Take a look at the great reviews I’ve received: https://clarity.fm/assafben-david
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