The first international trip usually feels bigger than it is. Once the passport, visa, money and first two nights are settled, everything else is just decisions that can be made on the road. This is the order to think in.
Documents before flights
Check passport validity (many countries want six months of runway), confirm whether your nationality needs a visa or an e-visa, and make two copies of everything — one in your bag, one with someone at home. Sort this before you book, not after, because it changes which flights you can take.
Money in three layers
Carry a little local cash for day one, a card that works abroad for the week, and a mental 'if everything goes wrong' reserve in your home currency. The point of the reserve is not to use it; it is to stop the small worries from becoming big ones.
The first 48 hours
Book the arrival night near the airport or with a clear transfer, keep the first meal simple, and do not schedule an attraction for the morning after landing. Jet lag, a new currency and tiredness are a bad planning trio. Give yourself one easy win: check in, eat, walk somewhere near, sleep.
What to leave unplanned
Day three onwards can be flexible on purpose. Your energy and interests after two days on the ground are a better itinerary source than any pre-booked list. Book the anchors, leave the rest to decide.