Instagram, as terrible and awful and invasive as it is, is probably the best option ATM. Artstation works much better for a portfolio though and is just a nicer site, there is not much audience engagemnt really and there is the double edged sword of it only being filled with finished work and highly polished work for the most part. Artstation does have a blogging section for people but it's kind of shunted out of the way and I don't see much engagement on it for those who use it. Deviant Art switched to a new awful format and I've stopped visiting it more than once a month or every two months and they lost a lot of artists who got fed up with them.