In Iceland, hitch hiking for shorter distances is convinient and usually successfull. We were able to get from Keflavík Airport to Jokulsárlon ice lake in about a week and visit all highlights around the main 1 round. Both locals and tourists gave us rides. When we wanted to go further to Hofn and above, we waited all day long without success. With tourism massively growing in Iceland and high price level in the country you can see many hitch-hikers waving theirs hand along the main round. Outside of densily populated areas, there are only tourist with rented cars and they are obviously not always eager to give you a lift. That is why and when hitch hiking becomes more complicated.
Bus transport is expensive. You can choose from two main companies – Reykjavik Excursions and Sterna. Sterna is a bit cheaper but Reykjavik Excursions has more lines and is more frequent. Think about buying a bus passport for the whole stay in Iceland, it may be convenient both in comfort and money. For Reykjavik Excursions, some passports can be issued only in Reykjavík, which is weird. There is quite a cheap connection from Reykjavík to Akureyri and back from Sterna (riding along the main 1 road) costs about 6 000 ISK one way. You can pay by debit and credit cards nearly everywhere in Iceland, even in buses in mountains. There is a free Reykjavik Excursion line from Reykjavík campsite to Keflavík airport once a day leaving in about 7:30. At Rekjavík campsite, you can find free gas containers and food for travelers.
If you want to get to less touristic places and outside of the main 1 round, you need plenty of time for hitch hiking or you need to rent a 4×4 vehical. Prices for renting the smalist 2×2 cars starting just under 100 Eur/day, if you take the car for at least 7 days, 4×4 vehicals are available for around 150 Eur/day. Gas costs about 250 ISK/litre.