How should a first-time traveller plan a Serbia trip?
Start with Belgrade, but do not let it become the whole trip by accident. Add Novi Sad and Vojvodina for an easy extension, or rent a car if the trip is really about mountains, monasteries and Danube country.
Answer
Serbia works best when you choose the version of the country you actually have time for. Belgrade gives food, nightlife, rivers, history and the rough-edged capital energy that explains a lot about the place. Novi Sad and Vojvodina soften the rhythm with cafés, architecture and easier day trips. Once the plan turns toward Tara, Uvac, Đerdap, monasteries or smaller towns, the trip becomes less about quick public-transport hops and more about route design. A first visit does not need to prove every region. Belgrade plus one strong extension will usually beat a scattered loop that spends too much of Serbia on buses.