The 750ti is recommended to have at minimum a 300w PSU.
If you go ahead and try it know that you might be putting too much draw on your PSU and that could cause a system shortage (or total failure). 250w PSU's aren't typically very high quality, so taxing them isn't usually a good idea. It MIGHT work, but you are definitely running a risk if you try it.
I don't personally recommend it.