It seems you want a mobile app as well as a web app with features you described. First of all, you need to know that a single seller/user can not provide all of them, you need a team of developers. For high-quality design, you also need a designer. As well as a system admin to maintain your server.
So, you need -
- Backend Developer.
- Web developer.
- Andriod Developer.
- iOS Developer.
- System Admin.
- Graphic Designer.
You don’t need 1, 2, and 5 if you manage to find full stack developer. There are developers who can do all of them but the quality is poor.
The first task is to find someone who has knowledge of all tech needed(don’t have to be an expert in all of them) and has the ability to lead a team. The team leader must be trustworthy and qualified. How successful your project depends on team leader.
You and team leader will decide whom you want for your project. Do some research before starting the project like how much time needed, costing, etc.
This is enough for starting. Later you can decide what you need based on the need of that time, for example -marketing expert, etc
I hope this helps.