Unless you like the farkling thing I would put my clothes in a garbage bag, put the garbage bag in a soft bag and take off. Camping gear on the front rack and a two gallon jug strapped to the floorboards. If the bike is in good shape and you travel light you will enjoy the ride, not spend a ton of money on bags and gain lots of experience. From that you will get a much better idea of luggage needs for the ride to Tierra del Fuego.
A traveler I greatly respected described the Vespa two stroke as the best touring platform among motorcycles and my experiences have borne that out. You will have great fun.