Determining who to follow is a challenge in this topic. Many of the Instagram accounts that appear in "social media marketing strategies" are businesses trying to sell marketing.
Here are a few to follow, and analyze if their content fits the curriculum.
https://www.instagram.com/socialmediamarketing091/using the hashtag #socialmediamarketing strategies resulted in 27K posts to sort through. This is probably a better search than searching through the instagram accounts looking for free advice.