On Facebook. If you're going to buy likes you might as well buy an ad with the Paid Post Engagement objective. You can promote your posts for as little as $1 day, so no matter how much you're spending on "post likes" you're going to get better engagement if you just go straight to the source.
I’m assuming you’re talking about Facebook. In that case, I’d strongly recommend that you don’t buy likes. That’s probably not what you want to hear, but consider this: When you get a bunch of fake likes from fake fans, your average post engagement rate will go down the tube. After all, these people (if they're even real people) are not actually interested in your stuff. When your engagement rate plummets, this will eventually be picked up by the Facebook algorithm, which will then push your posts down the News Feed. Also, if you eventually get some real fans liking your page, and want to target them with paid ads, the fake fans will still be on your list. If you have a lot these bought likes, it makes it much harder, if not impossible, to see how well these types of ad campaigns are doing. So, I agree with Sharpay. If you want to spend money on Facebook likes, you might as well spend it on a legit engagement campaign on Facebook itself. With that being said, if you’re just using the page as disposable social proof, I guess it could still be a viable option, depending on the prices. In that case, I’d check places like BlackHatWorld’s social media marketplace. Even though I’m skeptical, I’ve even seen some posters there claiming they can sell you real likes from real people.
Agree with the others, there is no point of buying followers, if you want to build a real page - this messes up the statistics for the page and your audience profile. If you still want some cheap likes look on blackhatforum
Just know that likes that are bought or through likeforlike or some other service are absolutely dogshit and only hurt your page. It's very simple really, but people still think there's a shortcut and don't realize their page instantly sucks once they start buying likes.
It's better not to buy likes in order to promote your page as in most of apps such likes can be banned and it can be seen that likes are not from real people and it will do nothing good for your page.