A used card like a GTX670, 680, 770, 780, 970, HD-7950, 7970, R9-280, 280X,290, 380, 390 would be a huge improvement over the IGP. But you will need a power supply to match as some of these cards do use more watts.
Some of the new ones like the GTX1050ti, 1060 use little power and will even work with molex to pcie adapters. Some evga cards and others come with those adapters too. The RX470 uses a bit more power but is still less than the older cards.