In answer to some questions from a number of replies to posts, here are some tips I have picked up as a Newbie to Crytocurrencies.
There are other exchanges besides Coinbase that are deemed by others to be safe. (I'm a newbie myself, so I can only share the ones I have read about from the "gurus"). The top ones appear to be Bittrex and Binance that trade in many other coins. You need to transfer BTC to them in order to trade (which is an extra step with a fee attached to the transfer) and it takes some time (maybe hours) for the transfer to occur until you can trade it for the coin you want to buy. By that time the price will have changed so you may want to have a small amoutn of Bitcoin BTC moved to an exchange where a coin you are tracking is traded and the price you want to buy can be followed.
Some exchanges want you to give them access to your bank account info for ACH transfer of purchases, which is another security risk and may still have delays in purchases or in having control of the coin you have purchased.
Remember all transfers of ownership in the cryptocurrency world have to be recorded on a public blockchain and verified by multiple computers, and that take time -- sometimes hours.
The KEY in all of this cryptocurrency dealings is only invest money which you may totally lose. A great money management idea (which anyone who gambles on stocks, 21, Roulette, etc. knows) is that if you make enough, then take your money off of the table and let your "winnings" ride. Remember, no one knows which cryptocurrency (or which stock or other investment) will make a profit for you.
Also a good suggestion to consider is that you use wallets that are not stored on the exchange where you bought coins, as an added level of security. Be sure to print out a physical copy of the backup phrases or keys or word groups, so in the event of your computer crashing or your photo being lost, you can recover control of the wallet. And keep those codes in a secure place, as anyone with those codes can transfer them to where ever they want.
So the Sequence of Buying and Selling Crytocurrency is to have a site such as CoinBase or GDAX to buy Bitcoin. If you want other coins then you move some of those BTC to an Exchange, such as Bittrex or Binance. The third Level is to have private Wallets such as JAXX or ABRA to store the coins you are not actively trading since you will have to transfer them back to an exchange to buy or sell them. Each wallets will hold only coins that they specify.
Hope this helps some of you. A vote would also be appreciated if this info does help you.