It's hard to say.
What is the true goal?
Do you want every song the same volume? For a worship service I would think this is not the true goal. I'd want some songs louder than others, depending on whether it is playing behind someone talking, someone (or a whole choir) singing, or if it is a feature piece, or maybe a reflective moment.

If you want them all the same, some would suggest using 'Normalize'. This can get things close. RB/PT have a normalize function as do most music apps. This feature usually just adjusts the highest peak to be near zero on the VU. Highlight the whole WAV file, then use Edit-Aduio Effects- Gain Change and look at the Pre Normalize and Peak Limit options.

There are also other meters to measure perceived volume.
RMS meters sometimes help to get closer here.

In a basic system I would open the resulting WAV files using MediaPlayer or similar and listen to them in order, thinking about the application for each.
I'd also set the Visualization to Bars and Waves so I could 'see' the levels of the different frequencies as I listen. Make notes as to which needs adjustment.

Then I'd open the same WAV files in RB (or any other DAW) and use some kind of gain adjustment on them. PGPeakLimit, Ozone, one of the WAVES limiters or whatever.

Rinse and repeat until you have what you think you need.
Then at the worship service, listen and learn for next week. <grin>

Make your sound your own!
.. I do not work here, but the benefits are still awesome