Of course we buy things/ do things for our pwBPD hoping that they will enjoy whatever that is.
I usually don't try to make it that big of a deal, otherwise when they don't share the same happiness I may get upset. Obviously it still hurts when they don't like it all that much, or when they complain about the gift. However, I can deal with them not being all that excited, but still can't accept being scolded for something (maybe not related to the gift, but in a pwBPD's mind they won't
not make a fuss of "problems" just because you've just been nice to them).
I keep on telling myself, I give something because it's an act of goodwill. I cannot control his reactions. I even had the guy at the Apple Store trying to convince me that if I buy somebody an iPad, they will likely just be really happy about it. I don't think he has lived with a pwBPD before
I also agree with eeyore that you will need other people to validate your actions, whether it's the Apple Store person or a friend. You will also need to validate yourself.