Buying for a fly angler is harder than buying for someone who throws a spinning rod. Almost every big piece of fly gear is matched to a line weight. Buy a 5-weight reel for someone who fishes a 4-weight rod and it goes back in the box. Most gift buyers have no idea what their angler fishes, and asking gives the surprise away.
So this list sticks to gifts that work no matter what rod is in the closet. A tippet dispenser that holds five sizes. A tool kit. Forceps. A fly box, a box of flies, a wooden net, a chest pack, a tying kit and a good book. The one exception is a full starter outfit, which only makes sense for someone who wants to start and does not own a fly rod yet.
Tom put this together from published specs, Amazon buyer ratings and AI-assisted research, not from testing each item himself. The ratings quoted are Amazon's. The table sorts every pick into a relative $, $$ or $$$ band so you can match a gift to your budget without a price that goes stale before the holidays.