I have a few videos on my youtube channel that talk about current profitability and prices of GPU (my channel is https://www.youtube.com/channel/UCOaivq7siMxHUQUCKtLxSFg) but honestly my favorite for raw knowledge is Voskcoin at https://www.youtube.com/channel/UCT44w6854K62cSiwA1aiXfw he really shows you how to build rigs, they are NVIDIA mind you, but you can pretty much do the same with AMD swapped in if you want to go that way. I highly recommend him if you want to learn the hardware side.