Like a number of others on here I went with the Samsung Pro Endurance 128GB for my second microSD card that I have so I can switch them out on occasion and still have coverage. Here's the info on this Samsung card which is designed to work in dashcams.
MicroSDXC PRO Endurance Memory Card w Adapter 128GB Memory & Storage - MB-MJ128GA/AM | Samsung US Operating temp ranges from -25C/-13F to 85C/185F and can be found at the bottom of the webpage. My other microSD card is a Blackvue 128GB (we have a Blackvue dashcam in our MS) and it's worked flawlessly for us in that usage.
128GB is a good amount of storage space as the TeslaCam buffer (5.4GB) will overwrite itself. Each saved file (manually from TeslaCam or automatically using Sentry mode) will be 0.9GB. The real variable in storage is dependent on where you park with Sentry mode on as it gets triggered by sound vibration but also motion around the car. A busy parking lot depending how you park your car can see a number of files written. But easy enough to swap out cards occasionally and delete them. Reformatting the card occasionally should also be done.