There are many best gifts that can be given to mentors because they have great services in teaching us. Generally, trading mentors don't expect anything other than the payment they set when we want to learn trading, but as a form of gratitude even though we pay them there are times when we give something more which will make our relationship with them stronger.
Yes, payments are more than enough for the service that they offer. If there are legitimate trading mentors and you've been able to take all of their teachings then all up to you.
Can be additional payment, a token of appreciation like mugs, cap, etc.
Those simple things will be appreciated by them. Because a real mentor makes a lot of money from trading itself and they can buy everything unless they're just plain mentors that do not trade at all.