I got a request recently to give a Geologist's 'Field Trip Guide to Iceland'. Fortunately for you, I just finished putting one together... so let's chat geo-travel!
A good trip to Iceland requires your own car and at least ten days to see everything. This guide is for a non-4WD, so I won't be sending you off into the highlands. If you do have highlands questions, feel free to DM.
Another quick note before I get into it: you'll be doing a LOT of driving and will be a bit tired, but I promise it'll all be worth it. I'm also starting you out right away... no breaks here!