Do you mean multiple trades within one asset or across multiple different coins? I don't really see the problem with running multiple trades and strategies in the bitcoin market as long as you can fully understand them, stay on top of them and most important you make money from them. But if you are running multiple strategies with different crypto coins than it could become too much to handle and staying uptodate in all the markets at once is difficult. In my opinion it's better to fully focus on one coin instead of spreading out our time and money if we are trading actively. In case we want to invest only and not touch our positions for a while, I would recommend to spread our money out. But in the end it comes down to what suits us best and where we are the most profitable. From what I read from you it sounds like your friend is struggling in his current setup and it would make sense to change his trading approach.