These are all estimates from my 4 years of owning a 125cc scooter:
100NT for gas every week (this will solely depend on how far your work commute and how often you have to run errands)
500NT for oil change every 1000km (roughly once every 1-1.5 months for me)
1200-1600NT for insurance every year
800-1500NT for new tires roughly every 5,000-6,000km
I can’t seem to factor in any other things. It will really depend on the condition of your vehicle and if you need to maintenance it after the initial purchase.
Hope the above was helpful!