I've always taken a "Chinese first" approach with my work, and the same goes for social media. Here's where you might find me:
Weibo is not as influential as it has been in the past, but his is the best place to broadcast messages to the public. I still check in and post stuff from time to time.
WeChat is the king of Chinese social media, but it's more of a closed platform than Weibo. I maintain a page here simply for reference. Click on the button above an scan the QR code, or search for 大山侃大山 under "subscription accounts" inside the WeChat app.
Nowhere is the Balkanization of the Internet more apparent than in the separation between Chinese and Western social media platforms (and it's getting worse). I maintain a basic presence on these sites, but only a small minority of my Chinese-speaking audience is here at all.