We chose to rent a car during our week in Iceland. It wasn't the season in which we could rent a camper van, but if I ever go back in the summer, THAT is exactly what I want to do! It will be more adventurous and help to save money on expensive hotels. Just make sure your travel companion is someone you want to live out of a van with!
This itinerary focuses mostly on the southern portion of the ring road. With more time you could go much, much further!
Day 1 -- Arrive in Iceland and get a snack or two in the airport (incredibly tasty) but there is a grocery store right outside of the airport road where you can get some sandwiches and snacks for the road. This will be the key to saving money in Iceland: eating from the grocery store and not from big fancy restaurants.
Head south of the airport to check out the bridge between continents. This whole area has a good amount to see and is often forgotten since it's not part of the famous ring road that everyone knows about
Still have time and daylight? Since you're by the airport you have time to go to Blue Lagoon. Depending on how much money you want to spend, you have some different options of "luxury" during your stay there.
Day 2 -- Decide what you want to eat for the day and plan ahead! Your drive to Vik will be about 2.5 hours, but depending on the weather and your stops along the way, that could be more! You'll see lots of waterfalls that you will want to stop at.
We decided to stop at the Lava Centre to learn more about what is happening in Iceland: https://lavacentre.is/
Then we stopped at Selfoss to see the stunning waterfall. There are others, such as Gljufrabui, that we didn't stop and see. But you should check it out!
Stopping at Skogafoss was AMAZING. There were services in the parking lot, but if you have to pee in Iceland you should really plan ahead. Not all of your stops will have bathrooms :). Although my friend enjoyed the bottom of the waterfall view, I elected to take the few hundred stairs to the top and explore even more!
Finally we arrived in Vik at night. We stayed at the Farmhouse Lodge and the breakfast was good. It was a small hotel with just a few rooms and about 25 minutes from anything other than nature :). Beautiful location, but be ok with some isolation! Down the road is Reynisfjara, which I think people know from Game of Thrones? but honestly I just went there beacause it was beautiful! I spent over an hour there just watching the waves and taking in the scenery. We had dinner in a little restaurant in town that night.
Day 3- We got groceries and left for Jokulsarlon in the morning. I had wanted to see the black sand beaches with Ice blocks ever since I learned about Iceland. Our day driving in March was pretty treacherous. I think all cars have snow tires, but a bigger car might be better to rent. My winter driving skills were certainly tested this day.
We stpped along the way once again to check out waterfalls, beautiful scenery and drove near/around Vatnajokull. We didn't have a lot of time to do any adventure sports, but man do I wish I had done an ice hike over there. It was all beautiful, and there were areas for hiking too.
Spend as much time there are you can.
Once we got to Jokulsarlon we stayed in the very rural Hali Country Hotel. I had the fish for dinner and my friend had lamb. I can still taste that dinner it was so good!
Day 4 - Spend time in Jokulsarlon with the big ice blocks on the beach. It was amazing.
We spent most of the afternoon at the site for Geysir to see the very big and some of the little Geysirs. This area has everything (maybe even a gas station) that you could need. The prices might be higher, but it could be more convenient for you!
This day was treacherous once again with snow and driving, so we didn't get to see as much as we wanted to.
We spent the night in Reykjavík. We went to a fancy restaurant to conmemorate having saved so much money in Iceland!
Day 5: Saying goodbye to Iceland was hard, so we did it by visiting Gulfoss (Huge waterfall) and secret lagoon. Secret Lagoon isn't as famous as blue lagoon, but it's beautiful and a little less expensive. It was beautiful and lovely to be warm in the hot springs while it was cold and lightly snowing outside!
We ate a late lunch at a Tomato greenhouse that is interesting and famous. If you don't like tomatoes, you probably won't have a lot to eat here: https://www.fridheimar.is/en
Day 6: walk around downtown Reykjavík looking at some of the cute shops and the famous beautiful church. Your flight out will probably be late afternoon so this is the perfect amount of time for some quick exploring before saying see you later to a beautiful country.