focusing on only one coin will increase the chance of success and understanding the movement of the chart, after all what we are looking for is stable profits and one coin is enough right?
Focusing on one coin may not necessarily increase the chances of making profits but it decreases the potential loss of the capital, and yes it will help them to understand mand master the price tracking and get better predictions but making consistent profits either with one coin or many coin isn't a guarantee, we need a bit of luck too with trading to keep making money.
If a coin is chosen that is always going above its good record then it is better to choose with that coin and a lot of profit can be made from it. We should also look at other coins to see how they are perform, which will give us a good idea about them and from this, apart from one coin a lot of profit can be made from other coins as well. If we talk about luck, then it is a very good and bad thing, which supports it, then it takes it to a very good position.