Round for the new year, braided for every Shabbat, bread as a gift always works.
Challah, the braided egg bread, is central to Shabbat and Jewish holidays. On Rosh Hashanah it is traditionally baked round, for the cycle of the year and the crown of creation, and often studded with raisins for extra sweetness. Showing up with a beautiful one is a gift that gets eaten and appreciated on the spot.
A round challah from a quality Jewish bakery is a genuinely welcome Rosh Hashanah arrival. Bring it to dinner and you will be invited back. If you can bake one yourself, even better, a homemade challah is one of the most heartfelt things you can hand someone.
For a regular Shabbat, the classic braided loaf carries the same warmth. Bread you can smell before you see it, made to be torn and shared, is the definition of a good Jewish gift.
A holiday or Shabbat dinner host, or anyone whose table you are joining. The humble, always-correct thing to bring.
Jewish and artisan bakeries, especially in the days before the holiday. Or bake your own, recipes abound in any Jewish cookbook.