I have 2 nephews and 2 nieces to buy for and won't have any more to have to buy for. I have always spent whatever I have wanted on them and that won't change just because I have my own kids now. I much prefer to buy them useful things that may cost a bit more than buy them cheap crap. My sil has been the same with our boys.
When it comes to buying a present for friends kids I usually spend $30 on a gift.