At that age my daughter was similar. I always joked that buying toys was silly when sticks from the yard would do. She did play with the wooden train set. She liked to line up as many tracks as she could before touching the walls on either side of the room. Then we'd play with the trains. Her play was really scripted, but we could do it together, so that seemed like good interaction to me. She also liked sensory kind of toys. We bought her a mini trampoline, and various squeezy kinds of toys. She had a thing for awhile where she wouldn't sleep on her bed, but under the nearby crib (scared the bejeezus out of me the first time), so she got a bed tent for a gift. She also liked the hippity-hop and some large silk scarves. Mostly though, our daughter liked puzzles. She could do them insanely well at an early age, and it was always a good quiet activity. Books were/are a great first runner up.
My kids also like the sensory stuff. Some of the things they've liked are mini trampolines, hopper balls, sit-n-spin (actually, they have a dizzy disk which is like a sit-n-spin without the center post), and a mini moon bounce.
We've gotten some of our gift ideas from therapy catalogs. They're a bit pricey, but even if you don't get the toys through the catalogs, looking through a catalog might give you ideas for gifts. Some online catalogs you can look at are abilitations or TheraPro dot com.
We've had a lot of toys that never ended up getting used for their intended purpose. Between lack-of-interest and lack-of-coordination, it can be hard to find the right things for our kids!