So when do you tip a lady?  Before things start, after great service or only if she dies something above and beyond?
If you go over schedule time?
If so how much ir what percentage?

and you're asking that question?

every provider i've booked had a section on the website with gifts and gift cards they like

Which is never before a session. Before would feel like a up-charge. It’s like paying for VIP Service and not really knowing what it gets you.

"It's never expected but always appreciated." There are times I always tip, like for a FBSM date as that is the etiquette for that particular type of service. I don't usually tip for $1000+/hr women, but I do tend to tip when I do outcall and the lady drives/travels a long way, but doesn't charge me for that, as I think that is just general courtesy to do so.  
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Paying her for going over scheduled time really isnt a "tip" per se, as that would fall into the category of her being compensated her normal rate after the agreed upon time expires, but again, there are exceptions. I don't think most women have an issue with you going 5, maybe 10 minutes past, as long as they don't feel it is deliberate. After that point, I think a gentleman would ask what he then owes the provider. If she says no charge, then I would give her at least something extra to show your gratitude.
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But anything above her asked for rate with regards to an actual tip is on you. No set percentage, as that is coming from your gratitude and kindness of heart. Lastly, if it's FBSM, I include that in the envelope at the start and the other situations where I feel a tip is warranted, I just hand cash to the girl just before I leave.

I love to show appreciation to the people who genuinely care about me. Yesterday, I over tipped my friends at the nail shop & my local restaurant because I will repeat. As a professional lady of leisure I believe it comes back ten folds. It's nice to be nice.

I tip an extra hundred for ever 500. I tip beforehand, unless im seeing a new lady. Then i tip after based on performance.

Never = If I see a lady 3+ times a month (Quantity)

No hard and fast rule for me. If she gets a specific outfit or picks up supplies then I certainly will.

…is when I know I’ve provided a fantastic session that exceeded his expectations, and he’s so happy with it that he gives me something additional as a reflection of having had those expectations exceeded. It makes me feel appreciated and valued and like I’ve done a stellar job.

Why would you tip someone who sets her own rates?

If they go beyond service why not? If I ask for an outfit she doesn’t have and she gets it. That takes her time.

One lady started DATO on the other lady. The frisson I felt was so strong I almost splooged right there. DATY was fully expected, but as it turned out both ladies were really into each other and one thing just led to another. Given that this was an unexpected and very welcome enhancement, I tipped generously. On the rare occasions where I've been pleasantly surprised like that, yes, I've tipped.

From my side, there’s really no pattern. Some people never do, some bring a little gift when we say hello, and some just tuck something into my hand when we hug goodbye. I even had someone rescue me from a speeding ticket once 😅 It’s never expected, just kindness when it happens.

with lingerie cuz imma lingerie snob. Even first meets are well qualified and it’s only rare occasions that I don’t bring something spicy. I don’t tip with cash but nobody has complained about my strategy

I've tipped cash and gifts....

There is a breakdown between how providers talk about this topic and how clients on the board talk about this topic.
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According to providers, tips are rare. They aren’t expected but they are encouraged and appreciated. A lot of the time a tip seems to take the form of a gift. These gifts can range from something inexpensive (chocolate or bottle of wine) to more extravagant (jewelry and expensive clothes). Some providers do have a wish list for potential gifts if you are interested in giving one. Gifts aren’t necessary but providers to tend to remember them and appreciate them.
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While tips and gifts are rare, many clients on this board claim that they tip frequently and generously. Obviously there is a disconnect. Are the clients on this board not representative of clients as a whole? Personally, I think a lot of guys on this board exaggerate their generosity. So many guys on this board complain about rates and are bargain hunters. I doubt they’re going to turn around and hand out more money when they don’t have to.
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Personally, I don’t think tipping is required or necessary. I will sometimes purchase a nice gift if I want to show appreciation. It has never caused me an issue and I usually get great references. I consider escorting to be a professional service. This includes professions like lawyers, accountants or doctors. Would you tip your doctor? Also, rates are very high right now. If I’m booking multiple hours with someone charing $1,000/hour I don’t really see the point of handing them an extra $100-$200 an hour.
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There are some additional nuances. If a provider is independent I am less likely to tip. If a provider works for an agency or at a brothel, tipping might make sense since the house/booker can take a big cut. If I have a special request, that may warrant tipping. If I’m booking a very long date, I might tip. If I am taking advantage of a special or discounted rate, I may tip. Also the rate matters. If a provider is charging a high rate I am less likely to tip. If her rates are reasonable I may tip. However, I don’t tip frequently and it doesn’t cause me any issues. I’m still able to see great providers and have a great time with them.

I haven't replied yet here, but have in another thread.  I've worked my way up from zero the first time, and added a tip to the donation envelope over time to now be 15%, give or take, and it will be the same going forward.  The first visit with a new girl I may not add it to the envelope, but will tip at the end if I enjoyed the visit.  Then from there forward I may add 15% if I feel I will get the same level experience, or may increase it slowly over time if there is a question I may not.

I’m being truthful. If she goes out her way to get a specific outfit or supplies. I’ll tip something.

Those posting on the board, or more specifically in this thread, probably make up about 1% of clients. It's possible we do not represent most clients. I'm sure it's possible some are lying, but even if they are not it doesn't make us a representation of what most clients do. BTW, your answer is similar to my answer.

the quality of the session.  When I'm seeing a new provider for the first time, I will tell her at the time of tendering the donation that I'm giving her half the tip up front as a show of good faith that she will give me the best experience she knows how.  I also tell her we each have a job to do.  My job is to be kind and generous, and her job is to make me want to come back very soon.  This works unless the girl is simply having a bad day or is preoccupied with something else on her mind.  I keep my word and give the other half at the end.  Most have no problem with that now that they know me.  

I will say that imo there's an issue of tipping with a repeated provider that I think can put the client as well as the provider in a weird predicament.

I tip when I choose, and as much as I choose. I trust that my tipping is appropriate and generous. Moreover, it is always done out of appreciation and not obligation.

...only describe your tipping policy with genetic women.  Since you have so much more experience with TS women, what Is your tipping policy with regard to TS ladies?    

Id be happy to answer that question, even though its a loaded question laced with blatant homophobia. But ill bite, Torta.