Usually I simply buy and sell coins) So, I've desided to mine) I have 2 gtx 980. Is it rezonable to mine new altcoins by videocards or should I buy special devices for that?(I mean not litecoin for example).
As you have 2 gtx 980, you can use that to mine Ethereum. You just need a computer with at least two PCIE slots. Your power supply should be powerful enough, say, at least 800W.