If you simply want to buy and hold some of the top major crypto, the easiest and least expensive way is to open an account at PayPal. Paypal has some of the lowest fees for aquiring Bitcoin, Ethereum, Bitcoin Cash & Litecoin.
This is the easiest way, because you don't have to setup a wallet or setup accounts on one of the many crypto exchanges.
However, at this time, crypto on paypal does have some major limitations:
You don't actually possess the coin. Instead paypal "holds" the coin for you and you reap the gains or losses incurred while holding the coin.
Since you don't possess the coin, you can not transfer it or use it to buy something else. You can only hold and sell it.
OWNING, SPENDING & TRADING
This becomes a little more involved. In order to own and to be able to send/spend and trade the coin, you have to open an account on an exchange or you need to setup a "wallet". Setting up a wallet is the the most secure way of holding your crypto. There are basically 4 kinds of wallets:"
There are "offline" hardware wallets (Ex: The Ledger Nano), that usually come in the form of a USB stick or some type of small memory card. These are the most secure.
There are online independant wallet accounts (Ex: GEMINI) that can hold several different coins. (Gemini also allows you to purchase many of the major cryptos right into the wallet you create.)
There are online coin specific wallets created by the coin originators.
There are online wallets generated for your accounts on each of the exchanges.