Are there any hashtags I shouldn’t use?

Yes. Instagram holds the list of banned hashtags close to its chest.

You can guess some of these – think obscenities, obvious pointers to banned content (#NSFW); hashtags that encourage spam likes #tagsforlikes; hashtags around nudity (#tanlines), and then others that really don’t fall into any category (#sopretty, #newyearsday).

There is a list here by Kicksta : https://blog.kicksta.co/a-complete-list-of-banned-hashtags-you-should-avoid/ but be aware it is not 100% correct (#sunbathing is allowed for example).

If you have any doubts, just look them up using the search function on Instagram – you’ll see the usage amount (first picture below), then you’ll see a message come up (second and third picture). This means, it’s banned.