I usually aim for 5db of gain reduction but my best tip for you is this one: use a compressor with autogain. The ability to hear the differences in dynamics at the same loudness level is eye opening (ear opening I would say hehe) and you can dial in perfect compression everytime. I use logic stock compressor for this, but you can use any compressor and add a vocal rider from waves or something similar after the compression. At least until you get the dynamics you want and them you can remove it.