Instagram expert & social media strategy for building a personal brand

I have been out of the work force since 2012. I graduated with a degree in fashion & textiles, I worked as a designer, visual merchandiser & stylist prior to having children & would now like to return to the design and fashion space. I've recently been looking at positions in the fashion design/ interior design / styling field and realise that brands want to see one's social media profile and to see that one has an online presence. I do not, and don't know where to begin. To be clear my end goal is to work for a brand as a designer/stylist such as the White Company / Diptyque or Rixo, not to be a full time social media girlie. I do have a busy London social life, a fabulous wardrobe and cute children but have not had the interest prior to now to put it online. Now that I do have the interest and my future career depends on that, I would like some solid help with the direction of my personal brand, what I should be posting & doing without being braggy & annoying. My instagram handle is ms_gosia.