According to the most popular website about cryptocurrencies - the number of available currencies is well above 1000! If you are thinking that's too much to learn, don't worry, not many experts know what comes after the first 100, so you'll be fine learning about the first 10-20.
You can check the list of all cryptos, their price and the market capitalisation using this link: https://coinmarketcap.com/all/views/all/