Cellulite and skin tightening: Renuvion and Cellulaze. Which should be done first?

There are no good treatments for cellulite.
It’s a difficult condition to treat. 
Cellulite forms in areas where there is more connectivity issue bands that stabilize the skin to the underlying muscle fascia.
These connective tissue bands don’t stretch and when the surrounding fat layer is greater than the length of the connective tissue skin dimpling occurs.
Cellulite often worsens with weight gain. It is often made worse by procedures like fat transfer.
The best treatment is subsicion with or without adding small amounts of volume either with micro(small volumes)  fat transfer or fillers.
This can be done with a device called Celfina the  device is not absolutely needed.  Subsicion can be done with other surgical instruments.
I own both the Renuvion and the cynosure MPX “Cellulaze” devices. 
They have virtually zero impact on treating cellulite.
The Cynosure device was marketed for this purpose but the machine fails in delivery.
I don’t believe Renuvion claims to improve cellulite.
My Renuvion will go to a new home in a few weeks and my cynosure  is for sale.  They were both fairly underwhelming devices in my opinion.
Sometimes dermatologist have more experience with this procedure than plastic surgeons do.
I would encourage you to look long and hard for providers who have a proven track record with Impressive improvement for cellulite before spending thousands of dollars.  This generally means having lots and lots of before and after pictures showing impressive long-term results after treatment. 
The bottom line is that there simply is no good or great treatment for this condition.
Maintaining a low BMI and healthy weight is the first step.  In regards to treatment nothing is better than subcission.    This is only my opinion and others may feel differently.
Consider looking for providers who own the Celfina device and we have lots and lots of experience. That device is fairly costly so providers who use it will probably charge more than those who do subcission without it.
I suggest interviewing multiple providers both dermatologists and plastic surgeons who are interested and have experience with treating this condition.
Best, 
Mats Hagstrom MD