"Do you always give her a tip plus her donation ?"  No.

I don't tip usually. I have a few times.

The ladies web sites will most often say Tips are not expected but always appreciated.  

Most here will tell you they don't tip or like me they have a few times. It isn't the norm if you go by what guys report here. I have never had a provider I saw act like I was expected to tip. The few times I did tip they said, you don't have to do that. Then they said, Thank You.

Don't go to the session thinking you have to tip

If you want to read more responses on the subject, I suggest doing research on past threads by typing "tipping" into the search engine feature on here.

You'll find hours of reading on the subject.

I bring gifts.  Not expensive, but up to you.  Search for 'tipping'

Swim

tip your dentist, attorney, etc.?

It is often said the best tip is schedule another date.

When I first started out hobbying I tipped because I wasn't sure of the protocol and I didn't want to risk offending ladies if the tip was expected.  I came to realize that the norm is that you don't tip.