I often mix in some of the dried iguana food from the pet store. She LOVES that stuff. To the point that when she sees me coming with the jar, as soon as I open the cage she leaps out and lands in my arms then shoves her face down inside the jar! (The first time she did this it scared the crap out of me because I wasn't looking at her, I was looking at the food jar!)
I have used fresh dandelion from my yard, although I only used the leaves. Dandelion is my "Oh crap...I'm out of food!" backup plan. Haven't tried alfalfa yet.
Besides the collard and mustard greens, I usually mix in carrots, squash, snap beans, and okra. Now and then she gets some fruit like grapes or berries or mangoes. Now that I think about it, her diet is a heck of a lot better than mine!
The reason for my starting post was I figured the greens were providing most of the nutrients she needed. But I wondered if there were a few other vitamins or minerals that she needed that the greens weren't providing enough of, and what foods would help fill in those blanks.