Providers are women first and sex workers second, and they are every bit as disparate as any other group of people. There is no secret "provider gift", except maybe for money, and I am sure that is not the answer you are looking for.

I've been enjoying my ATF's fine services since July of this year, and was thinking about getting her a gift. Don't wanna go over the top, but also don't wanna seem cheap.

Any Ideas?

... then you know what she'd appreciate. Nobody else can help you with that. (*grin*)

If you get to the 11th hour and still don't know, a reasonable fall back is a Victoria Secret gift card.
$100 minimum.

you should pony up so she can spend an hour or two with me.

My default is the uncle same gift card, e.g. cash.  Green Dot is very convenient.  But, it is not terribly personal, is it?  So, why not ask her what she would like for Christmas, or if there is something she really likes or needs "within reason?"  Yer a good fella!

Any doucheclam with sufficient cash can walk into a jewelry store and buy something loaded with precious gems and metal.

It takes actual thought and knowing a person (and their likes and tastes) to get something they want that isn't expensive.

I bet she wouldn't mind a "shallow gift" that cost a fortune, especially one she could return. lol

I know it was just a question to get people talking. everything else was boring. I already know what she likes, just the thought came to mind to ask.

Right you are.  I see my ATF (UTR also) monthly.  I suggested that maybe an extra visit with a nice tip would be a good Christmas present, and she was very enthusiastic.  Low or no volume plus Christmas expenses = happy to see you again.

This is my lil secret, and I don't share it with many people (um, until now). I pay careful attention the entire year, especially closer to Christmas, when it comes to buying gifts. People randomly talk about what sorts of things they like and what they wish they had. If you're with someone enough, they talk about their hobbies and things they like to do. Pay attention to these little "hints" (generally not intended as hints) throughout the year. Use these as your basis for making a gift purchase.

Random examples from the top of my head:
"Man, I lost the remote to my laptop/television/car stereo and have still not been able to find it!" [gift: remote]
"I went to purchase the cutest lingerie set, but it was all sold out of my size! This is what it looked like..." [gift: the lingerie in her size]
"I'm trying to learn to cook more ethnic foods, any recommendations?" [gift: cookook]
"Wow, that restaurant you went to sounds great!" [gift: gift card or dinner]
"What a bummer! My printer broke and I'm having to use the school's computer." [gift: printer]

It's amazing the gift ideas you can come up with if you pay close attention over a span of months and just really put some thought into it.