MAcs suck....what gpu is in there?
Radion 580. I thought it was a decent hash rate to earn something overnight, albeit very small.
Ok. From what I gather I have two choices... go buy an Asic miner or build a windows/Linux setup, or just buy coins and sit on them.
I suggest you first try running with mining software other than minergate. What coin are you mining?
If as you say you have an AMD Radeon RX 580 in your iMac you should be getting decent enough hashrates to at least have some mined coins after "hours of running." Just search for mining tutorials on google. I suggest mining Ethereum.