I just follow one pair that is gbp / usd. I am very comfortable to trade this pair because it has a low spread and I also study its characteristics about a year. For strategy, I use two strategies in my trading ie for intraday, buy in and sell at high point then I use scalping strategy to take a chance when price reversal. I think you should use and master one strategy. But you can use more than one pair as long as it suits your strategy. So what makes you make money is actually your strategy and your signaling system. If your signal is functioning mostly you do not have to be constantly changing. Just follow them and be patient.