You may not need the kidney cleanse before you do the LF, BUT how do your kidneys feel? The Liver-Flush is very hard on your kidneys and if they already feel irritated, you may want to clean them first. Just make sure you are listening to your body! It is understandable that you want to move on to the Liver-Flush so that you can see results and get rid of your acne. If you hurt some part of your body by skipping steps, it may take you longer to heal than if you stuck it out and did them in order.
I didn't do the kidney cleanse and I am now having some minor trouble with my kidneys. I don't know for sure if the 2 are related, but unfortunately I am head-strong and have to learn things the hard way! ;)
Again, listen to your body! And if you aren't sure, talk to a doctor who believes in natural methods that can help you.