If you're buying an ad to gain followers, then from my experience - no.
If you're trying to drive traffic to a web site, or some other action then it might be.
The biggest problem with trying to gain followers from IG ads is that there's no direct way for them to follow you - they need a "Follow" button - instead, you get a button that really only links to external content. In order for them to follow you, they have to figure out that they need to click your avatar, hit your page & then follow you.
Keep in mind, too, that your ad doesn't show on your page. So you may get 20K likes on it, but it does nothing for your page. Best you can do there, if you use a bot like Mass Planner, is to set the ad as a scrape source - to either like / comment / follow users who interacted.
I'll never buy IG ads again with the goal of gaining followers. Doesn't work.