Yeah I think there's no right or wrong answer. Anyways twitter & Instagram works best for me. Whatever social media platforms you focus on make sure it's easy for artists to find your beat website URL.
Even though as a small producer I don't get much traffic on youtube I still focus strongly on youtube as well & I would urge you to focus on youtube too. Because when you upload quality beats every week and you are consistent with the quality youtube uploads it will pay off eventually & u will start getting a lot of traffic through youtube.
I would suggest twitter to all producers. Because that's the platform where it's very easy to connect with producers & artists and really start building relationships with these people. Same thing pretty much with Instagram. If you engage with these people on these social media platforms, for example, selling beats for these artists & directing them to your beat website will be much easier & selling your kits for these producers will be easy too.
However, if you haven't produced over a year I would suggest u to just keep working on beats & don't focus on these things yet. Even though you would get a ton of traffic to your beat website the traffic won't convert into beat sales if your beats are not that good yet.