Juliet, until you're sure of what it is you want I'd suggest holding off on the posting. Better to wait for clarity on what you want than coming off as unprepared.
Now, regarding your possible post: change it from
socially to just social media active; I've never seen it the other way. Why do they need to be proficient in sewing stretch wear? That might need elaborating on, as it sounds like what you might want is someone to sew for you. Otherwise, if you just need them to be familiar with sewing stretch fabric so they understand what you are doing, proficient isn't needed.
From your posting and reply to DF is what you are looking for actually a social media manager? If so that is a paid position and low end freelance starts at $15 to $20 hour. If you have them creating content for you it goes up from there. Qualified social media consultants are much higher.
And one last bit of preparation before marketing: You personally have made up all sizes you intend to offer as well as having had at least one other person make up each size? In other words they are fully tested by multiple sewists so you know they all work and work well.
Hope this helps! Good luck. Growing a business from scratch can be very challenging and humbling. You get to discover all this stuff that you didn't know.