"I have my graphic cards ready to start, where do I start mining and which is the most reasonable way to start it?"
You can't use a graphic card to mine Bitcoin anymore, those days are long gone, now you need an Asic miner to mine Bitcoin and they are very costly, also do not bother mining other coins right now because it's never going to be possible since Eth mining is no more, I have 6 2080ti and they give me 1$ to 2$ per day, imagine that.