A gravel bike. Being able to get serious but low-impact cardio, anywhere from sprints to long rides, is huge. Not only is it good for my physical health, it's a great boost to mental health. Exploring the areas around me on a bike is much more fun, environmentally friendly, and healthy than a car. It's also a great way to disconnect and give my eyes a break by spending some time looking at things that are far away. $1000 is a good target, with a couple hundred extra for pedals, helmet, other gear if you need it
Gravel bike was my favorite purchase in the last year too.
I was already mountain-biking for the last 15 years. Things got more and more gravity oriented, where rides mostly had been one long uphill and technical trails down. While this is pretty cool it got a bit monotonic over time.
With the Gravel bike I enjoy doing far longer rides and checking out places I hadn't been before. 70km flat on an enduro mountain-bike are rather cumbersome, but fun on the faster gravel bike.
