Artists' successes on Instagram
What size do you need to sell art or to be "discovered"?
Frankly, it depends on what you do.
Some artists regularly sell with 1,200 followers, some got a gallery with only 700 followers, and another one had an article with 261 followers - there is no rule of thumb.
But seriously, the better connections you have, the more chances you have to find that gallery, that collector or that curator interested in your artwork.
And, you need time to help you to find your ideal followers.