Kraken allows you to wire in and out dollars via a bank account. I usually buy BTC from Coinbase and then send it to another exchange like Bittrix, Kraken, or Poloniex. You need to buy just about any other coin in BTC anyway. There are wallets that hold other coins or you could just hold them in the exchange. Eden is a new wallet that will hold multiple coins but you need to know what you are doing. You hold the only key (called a keystore file). If you forget your password or lose the file (computer is stolen/gets fried) and you didn't back it up, guess what? All your money is gone. Do your research though. If you have any questions, hit me up. I'll try to help out.