I have a portal hub at my main base and I explore in cardinal directions. When I have to sail to a new island I build a new lodge with room for 2 portals on that island one that goes back to the previous lodge in that direction and one for the next island in that direction going forward.

I also have 2 emergency portals for islands that are extra long (takes more then 1 days worth of travel) that go back to the main base so I can sleep and rest. The emergency portals are labeled E1 and E2. The main portals are North, South, East, and West. The 2nd portal in that direction is North 1, the next lodge holds North 1 and North 2 etc.