Trading on only one pair, in my opinion, has more disadvantages than advantages, because trading on only one pair limits the trader's experience and, as a result, his ability to progress in the field of trading. Furthermore, the trader must learn about all currency pairs and deal with these currencies, commodities, and metals in order to gain more trading experience while also being able to successfully deal with the financial markets.
However, trading on only one pair has a number of significant advantages, particularly for new traders, because the newbie devotes his efforts to only one pair and becomes intimately acquainted with its direction, as well as learning about the most important supports and resistances in the pair to be able to choose the best areas to enter and achieve the highest possible profit in the financial markets.