Rent a car. There are a lot of roundabouts and gravel roads so get car renters insurance too. We didn’t go on to the gravel road areas much this trip. We just stayed on the main road. If you are renting a car make sure you check road conditions.
Before we headed to Iceland we planned out what we were going to do. Only staying for 3 days, we didn’t want to become over whelmed. Day 1 we got settled in, day 2 Blue Lagoon and the 3rd day we explored the town of Reykjavik and sought out museums.
Reykjavík has a lovely bakery just a block away from Hallgrímskirkja called Brauð & Co. Delicious fresh bread and croissants. If you are planning to drive to the museums, make sure to visit Asmundur Sveinsson Museum.