Instagram 101 for Business
Your first 9 posts should be done before you even start to try to build your audience, so when they do arrive they will see content.
Depending upon your niche, your content will be different.
Make sure to write either something about your picture and/or video then always use # Hashtags.
For example, if you are in the Make Money Online Niche You could use #MakeMoneyOnline #WorkFromHome etc......
I usually always capitalize each word to make them easier to read but it's not necessary.
You are actually according to Instagram's rules allowed to utilize up to 30 Hashtags, I highly suggest that you use all 30 to maximize your results.