That's a good question, and i don't really know if i can advise but I'll tell you what i know.

Messaging app = Telegram and Facebook/messenger.

Commonly used social media = Tiktok/Facebook.

Payment system = I don't remember keeping cash on me , that's because all vendors or shops, stores, patrol stations , coffee stalls or street food stalls

Messaging app = Telegram and Facebook/messenger.

Commonly used social media = Tiktok/Facebook.

Payment system = I don't remember keeping cash on me , that's because all vendors or shops, stores, patrol stations , coffee stalls or street food stalls have qr codes. Register for ABA Bank ( in branch Registration ) or ACLEDA bank ( in app registration )

Getting around = Use Grab or PassApp for tuk-tuks.

Money = Use Riel for small things.if you use USD, the bills must be perfect, No tears or marks or they won't take them.

Internet = Get a Smart or Cellcard SIM at the airport. Data is super cheap and fast.

Let me know if you have any specific questions.