Lately, I have been noticing frequent outages from Coinbase that made it impossible for me to make any trades.
So, I compiled a list of alternative exchanges(http://coingenius.io/exchanges) that you can use to make trades.
For me, personally, I prefer to use Gemini to buy BTC, and ETH. They have the best customer service (4 minutes response time), and you no longer have to wait 5-10 days that you’d have to with Coinbase. Your fund is available to trade as soon as you make a deposit which is great in a time-sensitive setting.
For altcoins, I prefer to use Shapeshift to swap between two pairs of coins or Bittrex for newer coins. If you’d like to participate in futures trading, I recommend using Hitbtc or Liqui. Let me know what you'd like to use! Thanks!