One post every day is better than posting whenever.
The key to growing any social media account is to post something every day. I am guilty myself in not be consistent with my posting, but all it takes is just one update, one photo to Instagram will help you see growth. For Twitter, just share your thoughts or retweet something relevant to your brand. Blogging is no different, keep posting and sharing and the people will come. Facebook you will become irrelevant and fewer fans will see your new post. One post every day is all it takes.