Mining Ravencoin with 3+ GPUs

Recently I bought a 3rd RX 580 to add to my mining rig. First off, I am using an ARESGAME 750W 80+ Gold Semi Modular Power supply. I have two inputs I can plug a PCIE cable in. I was wondering, is the rule 1 PCIE cable per GPU? Once I tried adding 3 GPUs, I ran into a bunch of issues and even tried using a Sata cable for my riser (temporary as I would much rather plug directly into the PCIE slot on my riser).

I currently have only two GPUs in the rig and mining without any issues. I bought 6 PCIE splitters and they are arriving today. Now I’m thinking I should upgrade my Power supply to a fully modular 1000W+ platinum for the future. Anyone have some good advice?