graphic cards and etc to built my own mining rig and I don't want to make any expensive mistake.
Trying to mine Bitcoin with graphic cards is one of the most expensive mistakes you can make. Mining with GPU's died in 2012/13. To mine Bitcoin now you'll need ASIC mining hardware.
I made a mistake when I said "
mining bitcoin". I know that ASIC are better for Bitcoin and GPU's for Ethereum. I'm not sure which one to choose yet.