You know that sound the agencies get on their pro level, national ads? It’s usually a mix of good EQ and simple compression. So keep it simple.
I like to run the raw audio through a limiter first. That is, after I’ve completed putting it together and dubbing it down to a master track of just vocals. The reason for the limiting is to bring it all up to the same volume level so it stays consistent throughout the ad or promo. For this you can use any Limiter Plug-In you have access to on your DAW. I’ll tell you that I always record everything I do on Stereo tracks. They sound better that way when adding effects. The channel strip I use for recording is generally set for a 4:1 compression ratio. Some VO guys/gals set them at 2:1 or use none at all. For the Limiting try these settings, but remember you’ll have to experiment to achieve the right levels for your system.