Istanbul to greek islands

There are limited links between Greece and Turkey. Depending on your island destination, it may be faster and easier to fly to Athens first; see www.skyscanner.com. By ferry, you can connect Ayvalik-Lesbos, Kusadasi-Samos, Bodrum-Kos, or Marmaris-Rhodes. [Additional] Within each country, I believe you can fly to/from any of these points, such as from Istanbul to Izimir to visits Ephesus, before departing by ferry from Kusadasi.

If you weren't trying to visit the eastern-most islands, then you'd need another ferry to the hub of your next island chain, and possibly a third ferry from there to your actual island destination. For routes between islands, see www.greekferries.gr or usually good summaries in the Lonely Planet guidebook.

I woof
You can also fly from Istanbul to Bodrum, which is a yaghting port. I took a seven day cruise from Bodrum (Barbaros Yaghting, which was nice). There are several other companies, many of them you can find under "Blue Cruises," for the Aegean Sea. Have fun planning!
Pam from Bath