By bus
The buses in Argentina pretty much takes you wherever you want to go. They connect the country, and pass through the biggest tourist places, and is a great way to see the country. It is also surprisingly comfortable. Some of the best buses I had in South America where in Argentina; they even serve you food!
It is worth noting that it is really expensive to take buses, because the distances are so big. This will take a huge chunk out of your budget, and sometimes a plane can actually turn out to be cheaper and more convenient, so bare that in mind.
By plane
Because Argentina is such a large country, a bus or a car will take a considerable amount of time. I’m talking 24+ hours of constant driving. For this reason it could be worth it to fly instead. There are numerous airports in the country, and there are flights that go to the biggest cities and tourist attractions, and can be worth it if you are short on time, and can afford it in your budget.
By car
If you’ve got plenty of time, and want the freedom that a car will give you, this is the option for you. It’s a great way of seeing the country, and letting you stop wherever you want and not be dependent on bus times or making sure there’s available tickets left. It doesn’t even have to be very expensive, especially if you are more people that can chip in.