When my DC were in primary, I found this issue a bit tricky. There was 1 known teacher and then the school had a big bank if TAs and lots of different ones were in the class at different times during the week. I knew some but not all and not even all their names.
In total, there could have been almost 10 different adults in the class over the week.
So with gifts, I tended to send a big box of biscuits or chocs for the staffroom. It felt more straightforward.
I agree with others that there cannot be a blanket rule on this. People have different attitudes to gifting anyway, plus different budgets. Everyone must choose who they wish to gift to, if at all. Choose who you think has had a personal impact on your child. If in doubt, a gift for any adults involved to share such as food is a good idea. Sending it for the New Year after there have been heaps before Christmas can be good and bring a small amount of cheer into a miserable January morning.
I agree that TAs are very underpaid. Yes, they often work very fixed hours, but many aren't full time and don't get paid in holidays and often are taking home less than £10k. Presents though aren't a subbing of salary. In my view someone doesn't 'deserve' a gift more becaue they are poorly paid or because they are well paid.
Where things can feel uncomfortable is where classes have a collection and money is divvied out between adults involved in the class. I can see how this can send a message to all staff about their 'relative worth' to the parents. Those collections are kindly meant and difficult to organise and also difficult to decide how to allocate. As a teacher or TA, personally, I'd not be expecting anything and anything given would just be a bonus. Avoiding comparisons or being too interested in what I personally was given or certainly what others have been given, is probably key to keeping all this in perspective.
It seems some teachers or TAs perhaps do get rather caught up in keeping tabs on what they've been given and what others have been given. Getting your sense of value from this kind of thing doesn't generally end well. Being pleased with what you get and not giving it too much thought is much better.
As is often said on MN, comparison is the thief of joy. It really applies here.