Giphy kind owns the market - I tried long back, but it's a real pain finding and curating this stuff. There's better tools now to curate it but Giphy has a monopoly because of their integration into Whatsapp and Android messaging natively.
It's hard to get in there because of Twitter as well, which ranks well for animated gifs. Plus SEO is tricky because there's not a lot of content around animated gifs, so it's a lot of thin content sites. And then there's the whole copyrighted content part of it - not sure how Giphy managed to create a business model around taking other people's content.