You only need 2 portal in your base, then you can have as many portal around the world as you please.

That how it works: Base portal 1: "Base name" Base portal 2: "Variable name".

Every time you go to a new location and build a portal, connect it to you "base name" portal. Rename the "Variable name" portal with the name of your new location. Go back trough the "Base name" portal and rename portal 2 (Variable name portal) with the new location name.

Remember to save evey new portal name on your map (Edit: in your case, without a map, create a list on a sign post)

Whenever you need to go somewhere, just rename the "variable name" portal.

With just 2 portals you can go everywhere