If you want to play more than League of Legends and source games (i.e. counter strike, half life, team fortress 2, etc.), you will need to upgrade both the graphics card and the power supply. The cpu is probably way more powerful than what you need.
A relatively cheap upgrade that will allow you to play any game on at least medium settings would be an AMD R7 260x (260x, 265, 270, 270x, try to find a higher numbered one on sale) combined with a 500W psu from Seasonic, Antec, Corsair, or EVGA. If you're partial to nVidia, then go with a geforce gtx 750ti.