Many travelers say Iguazú Falls is a must-see — consider allocating 2–3 days (including both Argentine and Brazilian viewpoints if possible). It's reachable by a short flight from Buenos Aires or an overnight bus if you prefer land travel.
Split time wisely between Buenos Aires and Mar del Plata
Buenos Aires can easily fill a week with sightseeing, food, nightlife and day trips (Tigre, Colonia/Montevideo by ferry). Mar del Plata is more of a beach/tourist town — 2–4 days is usually enough unless you’ll mainly be socializing with local friends.
Plan long-distance travel carefully — Argentina is very big
Buses are comfortable and extensive but slow; many recommended routes are long. For distant highlights (Iguazú, Patagonia, Bariloche) consider internal flights to save time, especially on a 2-week itinerary.
You can combine Iguazú, Patagonia and Buenos Aires in ~2 weeks — be realistic
It’s feasible to visit Buenos Aires, Iguazú and El Calafate/El Chaltén in a fortnight if you accept some in-country flights and tight schedules. Add an extra 2–3 days if you want less rushing and to allow for flight delays.
Watch the seasons for weather-sensitive plans
Choose months by the climates you prefer: June–July is coldest in Patagonia; Aug–Sept still cold but possible; Oct–Nov warmer with more pleasant conditions in Patagonia and hot/humid in the north. Iguazú is humid year-round but gets hottest in summer.
Be flexible with budget airlines and connections
Low-cost domestic carriers (JetSmart, Flybondi, etc.) can offer cheap routes but sometimes change schedules on short notice. Allow buffer time between connections and avoid overly tight itineraries when flying domestically.
Consider overnight buses and jungle lodges for experiences
Overnight buses save daytime travel and accommodation costs for long legs. For Iguazú, staying at a jungle lodge near the park enhances the experience (some travelers recommend lodges inside or very near the reserve).