I’d never suggest someone eat at Subway in Norway, or anywhere else if they can help it. A discount grocery store (like Lidl) is cheaper, and there’s always better, local options. Hostels usually offer free breakfast, you can horde some of that for lunch, and there’s probably communal dinners and free leftovers in the fridge. Also, most don’t check if you’re actually staying there.
Don’t avoid “expensive” countries. I spent two weeks in Scandinavia and the UK for only a few hundred dollars. If I never visited these countries because they were “too expensive”, I would’ve missed out on some of my favorite experiences. Eat grocery food, sleep on trains, and visit free sights.
A laptop isn’t really necessary unless you need to work. A decent smartphone will do you fine.
A credit card with no exchange fees (like Capital One) is your best bet for purchases. It also makes it easier to keep track of your expenses and earns points/miles for future trips. Definitely have cash on hand in both local and popular currencies (USD, EUR, etc) but don’t use it unless you have to.
If you do need to take out money, become familiar with your bank’s partners around the world. For example, Bank of America lets you take out money from Deutche Bank and Barclays ATMs for free. This is the cheapest, easiest way to withdraw money in local currency.
