Bittrex and Poloniex is enough for me to trade bitcoin and also altcoins because it is on the mainstream where most of the traders here use that sites so you can easily sell and buy bitcoins and also altcoins without having any problem. Just register on that site and then deposit your fiat money and then you easily buy and sell different coins.
i am doing trading in bittrex and poloniex as both of the sites is the largest market that i can found and they are really have many list of coins and the coins is really good to help me to make profit. i think to join with them is not difficult and we don't have to waiting too long so we can started to trade in that sites.
I use local bitcoin to exchange my bitcoin, there I can find the right price as long as I pick the trusted person, they have many payment options which is a good thing, and unlike the other exchange platforms I can buy the amount that I want, and they have an escrow feature so the chances of getting scammed are limited.