Instagram have an amazing feature in which you can save your favorite posts in an album for feature.
you can create as many albums as you want and no one will see those collections.
open your Instagram profile and click on collection page option like this
now you have 2 options
All and Collections.
now click on "Create Collection" option like this
now a new page will open up to write name of your collection album.
write any name as i write "Shopping"
and click on "Next" option like this
now you have a collections of your saved posts.
Remember: Only Saved posts
select as many saved posts as you want. i select only 3 posts and click on tick option to proceed further.
now you have a collection album named as shopping.
create as many collection albums as you want and remember "No one can see these collections" unless you allow someone.