What do you mean by buying shares in mining companies, are you referring to cloud mining? If it's cliud mining, then you can make payment in btc…. Just like genesis mining and I believe that all of them are accepting payments in btc. And trading is something else that you can do. All the trading exchanges are accepting cryptocurrency as payment. There are lots of things you can invest in with cryptocurrency, but be very careful cause most of them are scam. It would be better for you that you simply buy cryptocurrency with fiat and store in your wallet, that way you can just HODL and be safe and that's it.