Setting up a good sound system for a new local church is quiet straight forward. You can just get the basic equipment you need with minimal features.

Speakers:

There are various type of speakers with various functions depending on how big your auditorium looks. You have the monitors, sub-woofers, and the usual output speakers. you should contact a sound engineer to come take a look at your auditorium and tell you the number and type of speakers you would need.

Amplifiers:

many people call this the engine. it is quiet heavy. The number of speakers that you have will determine how many amplifiers that you should have. the amplifiers consume a lot of power, so you need to put the rating of your generator into consideration.

Mixers:

This is where you control the volume of all the sound equipment connected. he piano, guitar, microphones e.t.c. is connected to the mixer and their volumes can be controlled from the mixer. Get a mixer with plenty number of channels, so you can have many sound equipment connected to the system.

Speaker manager:

A speaker manager is not too important, but it is a very vital tool to properly manage all your speakers if you have many of them. You might want to mute or isolate some speakers; the speaker manager will make it easy to perform some of these functions instead of having to plug and unplug cables frequently.

Power Stabilizer:

You need this to prevent damage due to electrical voltage increase.

UPS(Uninterruptible power supply):

You need this to ensure that once thee is loss of power, the sound systems do not just trip off on their own; the UPS will give you some time to properly shut down all the equipment properly.

Channel stage snake cable:

Depending on the distance of the studio to the stage, you might need a snake cable as an extension from the mixer to the stage.

Mich stands:

You would need these for microphone sittings to prevent partial contact that might occur between the microphones and their cords.

I did not mention musical instruments in the above list, you can choose to buy musical instruments as your budget can carry. You basically need to just buy a piano(you can get 2 if you can afford it), bass guitar, rhythm guitar, drums and a konga.