Easy to google all the famous spots but you should also try the small villages in the Westfjords, go to Melrakkasletta and Kópasker in the northeast. The Eastern Region are a most and Þakgil close to Vík. Remember also to visit less crowded places in the highland like Strútur hut, Dalakofinn hut, Þjófadalir close to Hveravellir and more :)

The ultimate roadtrip around Iceland is driving along the ring road. Depending on how many stops you are planning it can take 3 day to 3 weeks ;-)

You find a map for a classic Iceland roadtrip with tghe best spots and places on this site: https://www.contrastravel.com/island-reise/die-klassische-runde-durch-island/