I want to build a bitcoin rig. Any advise? newbie here.

Alot of reading I believe is outdated and alot lose money or earn very little. I have 2x gtx1070 and 2xR7 370 sleeping in my cupboard that I will be using to mine.
It's very late to enter the minig game. Also, you would not mine bitcoin, but rather the altcoins and then trade in to Eth, BTC or LTC.
Quite frankly you would be better off buying LTC and then trading on the exchanges.
If you DO want to mine, I suggest this:
1. Learn about undervolting to save power. Cards like the 1070 and 370 can easily cut down to 70% power at minimum hashing loss.
2. Learn about bIOS flashing on your 370. You will need to flash the BIOS to save power while boosting hash rates by up to 25%.
3. If you are not a pro, use a simple tool like Nicehash miner to auto-mine and auto-exchange for you. You lose a bit on the pool fees but it's automatic and hassle free. It will also auto optimize and auto detect the cards.