Most of the top tips have been posted. Revolut is brilliant.
Have a multi plug adapter handy. Chargers and cables are your friend.
Medicine pack is a great idea, especially the bug spray. Be careful of local laws re OTC medicines. (UAE can be a mine field). They are touchy on codeine and I think ephedrine too.
I carry a door wedge in case the locks aren't brilliant - it does stop the cleaners from barging in.
Get into the habit of locking and securing your door.
Long haul flights may need compression socks. You'll know what works.
I carry very little cash these days. Main currencies are Euro, GBP and USD (if going further afield).
Wool fibres work well. They don't crush and can last many wears.
Unless you know the country well, bottled water is your friend.