Trading Cryptocurrency carries a high level of risk, and may not be suitable for all investors.The possibility exists that you could sustain a loss of some or all of your initial investment and therefore you should not invest any money that you cannot afford to lose.
There are 3 main currencies which you can purchase using paper currency.
Coinbase is widely used for purchasing these currencies.Once you have hold of any one of these currencies then you can transfer them to exchanges like Binance, Kraken etc to purchase alternate coins e-g TRON,RIPPLE,Verge,Golem etc.
It is suggested to buy either Ethereum or Litecoin to purchase alternate coins because they require less transaction fees as compared to Bitcoin and it will save your money.
Ethereum is more recommended because it supports more trading pairs.
You can either hold or do day to day trading on exchange websites.