You'd need to be front-end developer who is at least familiar with jQuery, preferably more. Maybe even something like React (super popular at the moment).
Back-end you'd be fine with PHP, preferably something like Symfony or Laravel. Back-end guy needs to be solid.
For quality assurance I'll make sure these developers take testing seriously and get a technical adviser that can check whether they're doing things well, someone who is not related to the project.
Project is inshort explained in the attached image.
Also, I don't want any Wordpress or something like that.