I have an old rig that I wish to make a mining rig out of... Just beginning with one gpu for now...

Config- Mobo : Intel Dg31pr, Pentium e5200 2.5ghz dual core, 4gb ram and 160gb hdd (sata 3.5"),

I am planning to buy a GTX 1060 6GB and a Corsair PSU(which I'm not sure which version would be best/cheapest for 1gpu)
Both might cost me around 550usd, do I really need any thing else to upgrade excluding the ssd?

And My question is which would be the best coin for quickest roi, I am guessing zec, if I go with zec how long am I looking, if not overclocked how much will I earn per day in zec(do not care about fiat)? If I have to overclock which guide would be the best for saving me some beginner's trouble?