your pc's full specs would be helpful.
i am gonna assume you want to upgrade integrated gma 950 only.
you can't upgrade integrated gpu. you can either get a new discreet gfx card or you can upgrade to a better cpu that has better integrated graphics.
if your motherboard has a slot for a discreet gfx card, get one that suits your budget and needs. a discreet gfx card will be much more powerful than gma 950.
however you might be able to get even more improvement from a new system altogether if your current system is very old.
if you're into integrated gfx you can get an amd a8 3850 llano cpu - it has a very capable igp. on intel's side you can get a core i3 2100 with hd2000 igp - it's weaker than a8 3850 but it gets the most basic jobs done. all of intel's recent sandy bridge core i3, i5 and i7 come with integrated graphics so you can get one that fits your budget.