This has a nice vibe, which I really like.
I think for the style, I would use the xylophone a less frequently, and less evenly, have them kind of come in and out a bit more. Their constant presence made it less ambient.
I think it actually detracts from what you did with the rest of it. I also suffered from "I have to add more things to make it interesting," when really, a nice static drone with gentle swells and occasional other elements would have probably helped my track feel more ambient, and would have given it more length and quality without as much effort.
Great work though. I like your choice of instrumentation and it does create the right atmosphere. I also like the way you have things mixed reverb-wise, it fills the space nicely. I'd love to hear you mix this track just removing some of the xylophone and turning it down in the mix (you could even give it its own reverb to fill the space more).