Hungary is a capital split by a river, a thermal bath in the middle of town, and a ruin bar that started in a gap and became a genre. Budapest is the trip for most people, and it is enough: Buda's hill, Pest's palaces, a sunrise on the Parliament, and a bowl of something paprika-red.
It is still excellent value by Western European standards. The forint is the currency — not the euro — and a thermal afternoon plus a dinner will not require a strategy meeting. English is common in the centre. A jó napot at the bath desk is still good manners.
Do the baths properly (Széchenyi, Gellért, or a neighborhood one), walk both sides of the river, and take a day train to Eger or the Danube Bend if you have the time. Lake Balaton is the summer extra. The rest of the country is wine, villages and a slower clock.
Eat lángos once, goulash that is a soup, and a cake in a coffee house that survived an empire. Budapest is a grand city that still lets you in.