Answer:
There is no one right answer, but never forget to treat them well. Never forget a kindness, and always show your appreciation.
I had one neighbor who used to cook for me. She would prepare the shabat (Sabbath) meal and almost always she'd make too much, so she'd come over and give me food all the time. I'd always thank her, tell her she didn't need to do that, etc. One day when she stopped by she asked me for advice about what board game to get for her about what board game to get for her kids (she had a lot of kids, which is common in orthodox Jewish homes). She knew that I liked board games. After she left, I had a brilliant idea. I went out and bought a nice board game, one I thought her kids might like, I wrapped and I gave it to her with a nice note. It was just something I felt like doing.
The people in your a nice note. It was just something I felt like doing.
That's just one example. You don't have to follow that example. You don't have to buy a gift. The people in your life who treat you well, particularly those who go out of their way to be nice - just make sure they know how much you appreciate them.
Hope it helps you.