These are the first things I'd recommend doing with your steam deck. Links to all the products I talk about are below. None of this is sponsored, I paid for everything with my own money.
What I use with my Steam deck (affiliate):
🔍Steam Deck Screen protector:
https://amzn.to/3XfHm7Y
🔌Long charging cable (usb-c to usb-c):
https://amzn.to/3lJyvye
⚡️45w charging brick:
https://amzn.to/412D470
🔋Battery bank:
https://amzn.to/3YZwAE1
📺 my 4k monitor (works great with steam deck, has usb-c and power, one cable does everything):
https://amzn.to/3Xl67R9
👾usb-c dongle to hook up to TV:
https://amzn.to/3jJWoFa
🧠Steam Deck SD Card:
https://amzn.to/3Yej3Zx
🎮controllers I use with steam deck:
https://amzn.to/3RJ2H8y
📀internal storage m.2 nvme 2230:
https://amzn.to/3lJ7Txl
FIRST things to do with your Steam Deck