So, I created brand new IG account and posted my pictures there, all with correct hashtags and some captions.
There is no such thing as "correct" hashtags. Find similar images that get the attention you think yours should get, and note the hashtags and (appropriate) user tags. Note what you think makes them special, and if possible, what other people think makes them special (might be noted in comments). Also note how long that account has existed, and how many followers they have.
72 pictures ... and got total of 3 likes.
You posted them within the past 24 hours?
I'm curious, what were your expectations?