Instagram is great for attracting targeted customers. But the biggest problem is you can't add links in the post. The links are added as text and are not clickable. I think following is the only best way to covert your followers to customers:
1. Keep posting quality content. Always post unique, catchy and "can't resist to share" content. Content must force its viewer to share. And by force I mean it must be AMAZINNNGGG.... It's not like you just wrote "share this or you will go to hell" :D
2. Use hashtags. Research about them. Use most used hastags like "followme" "instacool" etc. But use that are more relevant to what you are selling. When you type "#" inside description of your post, Instagram will suggest you top hashtags. Select the one that is relevant to your business.
3. Give your followers free content like Preview PDF book (or something else that introduce your offer) in the website link on your profile page.
4. With each post add a line like "Click the link in the bio to get the free book" or "To know more click the link in the bio" or something else.
5. When user clicks the link you must take him to a page where he/she enters his/her email and then taken to a FREE content or download.
6. You collected their emails. Now its time to send newsletters about your paid content. Send them in 3 days gap or weekly. Don't send too much mails otherwise they will report your email as spam.
This is how I made a good business from Instagram. I hope it helps you too. :)