I had to do a bit of research on the effect of DMAE on skin; I was familiar with its neurological properties. What I can tell you is that everything I've read emphasizes the fact that its effects on the skin and its sagging and loss of elasticity (effects advertised by skin care companies that offer it), have not been thoroughly researched.
The only thing I can recommend is for you to read up on DMAE and familiarize yourself with it before deciding to purchase it. As far as I've seen, it is not very cheap.
Here are a couple of excellent articles about DMAE: