WeChat is the daily hub: messaging, class groups, payments and campus notices. Add your university office and roommate contacts early.
Also useful: Alipay, maps (Amap / Baidu Maps or Apple Maps), translation apps, metro / rail apps, and Didi for rides. Save important QR codes and screenshots offline in case the network is slow.
Create a folder on your home screen for China apps so you can find them quickly during the first week.