I've used Retin-A gel, not Renova, but here's a trick that helps me make it go a bit farther...I apply it with damp or very very slightly wet fingers. If my hands are dry, they wind up absorbing some of the product, making it harder to get that pea size to get around to my whole face.
With that said, I do use a bit more than pea, since I use it on my whole neck too. I actually break out more there than on my face.
This works well for the gel, but not sure how it works for Renova or other cream versions.
I do know if you use too much, you can wind up upping the irritation.
I'd be interested to hear if this works for you though.
Marcy