I suggest you start with one rig. Build it, tweak it, learn how it works, find the pain points, and then decide if you want to spend the rest.
This.
I started mining 4~ months ago and nearly went 20k deep on my first purchases but common sense prevailed. Decided to build one rig and learn the whole process end to end.
Rig cost $2300AUD with 6x RX570 4GB Gigabyte Gaming cards (28.8mh/s ETH or 818h/s XMR) but its paid for itself. Sitting at about $4500USD worth of coins at the moment. I'm planning to use that to build another 2 rigs as soon as I can nail down some cheap graphics cards.
Start small and get the hang of it. I refuse to pay full retail for gear and only buy stuff when on sale
