They are tricky. I feel like the most difficult part is convincing the gift giver that you aren't unappreciative by any means, you simply don't want to accumulate stuff. Fortunately, there are plenty of non-physical gifts we can give. Gift certificates or agreeing to cook someone dinner are better options in my opinion. I've also accepted a meal out as a gift. Friends will just take me out for a latte. :P It's not too expensive and it's fun to catch up with them instead of receiving a physical gift. :)