I cannot stand fundraisers from the side of selling. I do not like bothering people and making them feel obligated to buy anything. I usually just put it out there and say if you feel you want to contribute or buy this useless item then feel free to do so.
When my kids had to do any of this - usually I just contributed more money. I honestly think it is unfair from whatever organization that sets up a goal to make you feel bad or to really hold you to that goal at all. Everyone has different situations - you could come from a family that does not have much money, or you do not have many family members or friends. So I can see setting a goal per person/family but not to pressure anyone to meet that goal or even discuss with others participating in such fund raisers.
On the flip side - I do not mind contributing to fund raisers - I almost always do - especially when it comes to kids - I cannot say No to them and now I guess it is payback as my kids are older. As long as I know the fund raiser is legit (and someone is not just trying to scam you) I have no issue to contributing.
As an aside some people even strangers can be surprisingly generous. My daughter did canning once for her softball team. --- I actually prefer canning as you just give money and not buy something you don't really want and then it is all money going directly to the fund raising -- anyway canning is when you have a can and basically just ask for cash, typically standing in front of a grocery store. Anyone my daughter was there with another girl and or course a couple of parents to supervise and make sure no crazies bothered them or stole their can - and some guy came by. He looked a bit shady then proceeded to pull out a big wad of cash and began peeling bills from his wad - he had to gave them like a $100 bucks.
The only time I personally do not give, is if some kid is just standing or sitting and they do not ask you (politely of course) - I feel they should learn to explain what they are raising money for and show some appreciation and a little work - I don't expect much just a little and a thank you.