- GLH is top priority. All of your cities are going to be coastal.
- Colossus also a good wonder, but Astronomy should never be delayed on island maps so it obsoletes more quickly than usual.
- Temple of Artemis also worth a mention, but never ever risk the GLH in order to get this wonder, GLH is simply too valuable to ignore especially considering you've got water defending you from barbs and mean AIs.
- Navy not as important as one would think, you generally only need some scout workboats (don't waste galleys scouting, they're for moving workers settlers and military around your islands, plus workboats cost practically nothing by comparison) 2-6 galleys and one or two caravels until astronomy.
- Compass, Astronomy, Economics, all excellent techs on these maps. Trade routes from harbor are very lucrative, astronomy gives you longer range intercontinental trade which is even more lucrative, and customs houses give you big multipliers on trade as well.
Keep in mind that colonial maint only really starts to add up after you have more than two cities on the same landmass. Don't feel obligated to smash in as many cities as possible because it will just cost you that much more in maint. Few landmasses on archipelago maps are big enough to fit more than 4 or 5 cities anyways, but keep it in mind.