the first get i7 is now 5 years old. Uses older outdated RAM, doesn't have USB 3.0, and may or may not have SATA III Too and is PCIe 2.0.
If you are going to be doing gaming, better to get the i3. PCIe 3.0, SATA III, M.2, USB 3.0, Higher clock rate, better at single treading, DDR4 etc etc.
If you have the money get the i3. Find parts for a first get i7 will be hard as none of it will be new unless someone just hung on to it this long (Which some people do. They buy out all kind of stuff when something gets phased out and sells it later).