Consider her personal tastes and buy something appropriate for the relationship. Check out what else she wears or try to remember if she has mentioned anything in previous shopping experiences. A watch is a very personal thing but consider specialty models such as for diving or swimming or high-end pieces made by Omega or Rolex.
Check out the newest hot restaurants, theater openings, symphony performances, concerts and other events that might fit your taste.
There does not appear to be a similar universally accepted gift guide or suggested list for dating anniversaries.
Some gift stores and websites have created their own lists of suggestions but nothing as widely recognized as the wedding anniversary symbol list first created by Emily Post in 1922.
If you want to make it real different, rent a cool car for the evening or hire a driver to take you to your destinations.
Giving a woman a piece of jewelry comes with a certain feeling of affirming you are in a serious relationship.