I'm a teacher and in our district, we cannot accept a gift valued over $25. We are public employees and big gifts could be seen as "bribes" I guess. And personally, I've always felt uncomfortable with any gift more than that.
You don't need to buy for all of the special area teachers (art, music, etc.). I'm a reading specialist and I rarely get gifts from kids. Doesn't bother me at all. What some families at our school do is bring in treats for the teachers' lounge that everyone can enjoy. We really appreciate something that isn't sweet. Breads, fruit, veggie trays, or meat and cheese trays. But if that is more than you can afford, no one will think any less of you.
My kids have always had a para or teacher's aide in the classroom. I've never given anything to them because they have usually been 1-1 staff for a specific student (not my child). The one year my daughter rode the bus, I didn't give the driver anything.
I'm planning to give each of my kids' teachers a $20-25 gift card to Barnes and Noble. And maybe a loaf of bread if I get it made. For gymnastics coaches we spent about $5 a piece on fun socks. (They both wear fun socks around the gym.) For Sunday School teachers we will probably give $5 gift cards to our local bakery and maybe an ornament.
I would limit the gift for the teacher to $20-25 at the most. If you do want to give to the teacher's aide, I would give half that amount. Personally a gift card for cosmetics would go unused by me. I don't wear much makeup and don't buy expensive makeup ever. I would stick to book stores, craft stores, teacher supply stores, coffee shops, Target, etc. Definitely don't give the teacher coffee mugs, apple decorations, etc. We get tons of it and mine usually ends up in the garage sale box.
Teachers never expect gifts from any of their students. The thought is nice, but I've never felt any less for a child who didn't bring me a gift or any more for a student who brought a huge gift.
The best Christmas gift I've ever heard of a teacher getting was a first grade teacher I taught with. One of her little girls brought her a very pretty gift bag. Inside was a pair of beaten up, stinky white flats. She told her teacher that her mom never wore them anymore and she just knew that her teacher would love them! I think about that anytime a kid hands me a gift bag. Just hearing that story is the best Christmas gift I've ever gotten as a teacher!