This will depend a lot on why you want to get out of photography.

If you just want to learn how to compose a scene, direct a model for portraits, or simply record a moment in time, there’s nothing wrong with a cell phone.

If you want to learn the exposure triangle (shutter speed, aperture, ISO), you might want to get something where the lens has a manual aperture ring.

There’s a lot to consider in regard to technology and the weight / bulk ones of the camera. An older DSLR will certainly take great photos and help you learn photography, and come in under your budget, but it’ll be slower and heavier. Something with fast autofocus (great for sports and wildlife) could easily push past your budget. It could be argued that a camera with manual focus would be a more engaging picture taking experience; if that’s what you want.

Personally, I’d look at something like a Fujifilm X-E2 with a the Fujinon XF 35mm f2 lens or Fujinon XC 15-45mm lens. The camera has some advanced and fun features but with lots of manual controls. The 35mm lens is fantastic and has a manual aperture ring. The 15-45mm lacks an aperture ring but it’s small and light and allows you to adjust your field of view.

Edit: I just saw a couple X-E2 cameras on eBay including an 18-55 lens between $800-900. The 18-55 is an incredible lens but I think too big for that camera.