As it was mentioned before, it would be bettter to focus on one of the major currency pairs that are most popular among traders. First of all, such pair have sufficient volume, so there would be no huge spikes or slippage due to the lack of liquidity. Another important point is that it is much easier to find information on fundamental aspects impacting prices of major pairs, rather than for exotic ones.
By the way, you can also pay attention to commodities available through CFDs, provided by brokers: XAUGUSD and XAUUSD. It is easy enough to analyse them, and price patterns they form could be easily identified. To my mind Gold is one of the best instruments for newbie traders: it is not too volatile, and all price patterns on its charts look just they should be. It is also important to mention that you will be able to switch to trading commodities (as futures) when you would like to increase your size.
Another important advantage of popular pairs is that they could be used for backtesting strategies while it could be difficult to find historical data for exotic pairs. For example, you can use special backtesting software like Forex Tester to check the performance of your strategies using historical data provided by the brokers. It is also useful to find mistakes and improve your strategy.
So, you can focus on one pair or create a strategy that would work fine with several currency pairs.