In this case, I'd say「どういたしまして（you’re welcome）」is the most common response.You can also say 気にしないでください。（don’t worry about it）気に入ってもらえるといいのですが。（I hope you’ll like it）役に立てばいいのですが。（have use of it）However,問題あり...
Well, you can be a part of it! I have something edufire likes to call a ‘Superpass‘ to give away, although personally I’d have called it the ‘Viking Pass’, because it’s just like one of those all you can eat buffets in Japan – only it’s for the mind!