See how I'm saving $124 this year on my Proactiv ordering.  Maybe these tips will work for you, too!

Make complete systems out of your extra product. 

My Proactiv order shipped every 8 weeks.  I have 3 extra lotions and 1 extra toner which cost me $64.  I ordered 3 cleansers and 2 toners to make three complete systems -- cost:  $75.  Normally, three packages cost $138.  I realize by ordering separate products, I spent a dollar more, but I didn't waste 64 already-spent-dollars, so it was worth it.

Downgrade your shipping frequency.

Since I have a 6-month Proactiv supply, I downgraded my shipping frequency to once every 16 weeks.  Ordering half as often will save me $135 for the year. 

$135 saved + $64 not wasted - $75 for individual products = $124!

Downgrade your package. 

If you purchase a 4 or 5-piece system, try backing down to the 3-piece system, and see if it works just as well.