What are the “must buys” with the Switch 2?

I want to get a switch 2; I will mostly be using it handheld bc I work on the road. What are the most important things to buy with it and specifically which ones? I never owned a switch 1 btw and haven’t owned a portable console since a PSP.

For example: memory card, which one?

Travel case?

External battery?

Anything else??

Thank you :)