You don't need i3 and 8gb of ram. If you are focused on gpu mining you can go with celeron g1820 (ones i use for lga1150 socket) and 4 gb of ram. There is no need to spend extra money since those don't impact mining performance. Anyway based on your questions it doesn't look like you did much research on gpu mining. Maybe is better to make 1 rig first and then if you are able to manage it expand ?
I have 2 rigs doing their job for two months. I've bought i3, because of the resell value (easier to sell if I stop mining) + one experienced miner told me, that in some cases hashrate is going down due to slow cpu and low ram, so that is why I use 8GB of ram. Now I see, that this is too much for ethereum at least. I heard, that zec miners with slower cpu's had lower hashrates.