For variety of coins, Bittrex. You can also open accounts on various smaller exchanges that list specific niche coins. For comical leverage on the big coins (u

For variety of coins, Bittrex. You can also open accounts on various smaller exchanges that list specific niche coins. For comical leverage on the big coins (up to 100x) there's Bitmex. You'll need to sneak in through a VPN if in the US. For fiat onramps, Coinbase, Gemini, or Bitstamp. Avoid Kraken at all costs, unless you really hate yourself. You have to roll a Natural 20 to have an order succeed there.