Is it better to focus just on one currency pair? Or is it better to focus on as many instruments as possible? I don’t think there is a simple answer to these questions, it all depends on each trader, but there are certain guidelines that you can take in consideration to help you feel more comfortable with your system, which will help you trade with more discipline and at the very end, get consistent results.
Monitoring only one or two currency pairs/instruments
For newbie traders, this is definitely the way to go. As you start looking at charts, you could feel overwhelmed by the amount of information you could get by monitoring many currency pairs, sometimes it is even difficult for veteran traders (go figure), so you need to be careful if you are a beginner trader.
So as you start getting acquainted with charts, the Forex market, etc. Probably the best thing to do is to focus only on one, two or three currency pairs. This way you will get to know each currency pair better (each one has its own personality), trading ranges, spread, etc.