To get your performance out to an audience you are going to need a PA system. Systems start from a very basic level to the huge concert size rigs so choosing your system requires careful thought.
The system you need will depend on the number of channels you want and the average size of audience you will be playing to and it's also worth thinking about what you may need in the future.
On stage, you may want monitors to give the players a mix of what the audience is hearing. Monitors are wedge shaped speakers that are designed to project the sound up to the player. A basic setup will be a powered monitor with a built-in amplifier and maybe an extension speaker. Peavey and Laney make a good range of monitors suitable for any setup.