The world of forex is a big one and there are lots of options. I cant say which one is the best because there is a lot more to it than that.
It depends on your style of trading. Do you want to day trade or take longer term trades? Do you want to be glued to the charts or be able to relax and take longer term trades? The choice is yours.
Some signal providers offer signals off the 15 minute to 1 hours charts. Some use a longer time frame like the 4 hour or daily.
From my experience its a lot easier to make money off the daily chart as the signals are a lot stronger. The downside is you have to wait a lot longer for them to form so you will get fewer signals.
The choice is your, whatever you decide, try to find a signal group that offers a money back guarantee. That means they believe in their signals.