Here is an easy way to make money if you don't know too much about coins.

1) Find a newer exchange that doesn't have a lot of people.

2) Go to coinmarketcap and open that exchange's page e.g. https://coinmarketcap.com/exchanges/cryptopia/

3) Make sure you have BTC selected as the currency.

4) Go down the list from high volume to low volume and find a coin that trades at substantially different prices on two exchanges. For example buy/sell 0.0001/0/0002 on one exchange and 0003/0.0004 on another.

5) Look at the histories of that coin on both exchanges and decide if confirmation times allow you to be pretty sure of making money.

6) Look at depth on both exchanges and make sure it looks adequate in both directions.

7) Never risk more than you can afford or need to risk. On low volume coins traded on obscure exchanges you could walk into a trap so avoid exchanges known for setting people up, e.g. exchanges that list overtly bad coins.

Arbitrage is still wide open in crypto and a good way to learn about coins, since you should research a coin before you arbitrage it. Anybody could have made some program to arbitrage all coins across exchanges, but I guess the experts are leaving low fruit for new people.

Arbitrage provides a service, it lowers prices and keeps predatory trading in check, and can also be profitable.