It depends what you're liking too, if you're liking posts in #fitness for example, don't expect many followers, those type of hashtags are full of spambots.
That's true. You should target people who like the desired hashtag, rather than people who post. If you're in the fitness niche, for example, you should (firstly tailor your niche to be less broad) like photos of people who like #fitness photos, instead of liking photos of people who post the fitness hashtag.