LEEEEGGS

Might as well finally get this up here and get some words before I start fixing.

Just want some crit on digitgrade legs I made last year. The foam I had done for a while but wasn't sure I was going to use it until I was surprised with an offer to Otakon then I finished them in less than a week and I freaked out having no clue what I was doing. They came out better than I expected but there is still SO MUCH WRONG. Mainly the wrinkles the first test pattern fit but was tight and I feared seams would pop, added about an inch, too baggy, the third I cut half and it fit, I could move without fear but unless pulled up fully I got wrinkles.
I know I should add darts but I don't know how to execute them, the most in need being at the knee. The back side mainly tended to wrinkle when they started to slip which I am hoping a belt to hold them should fix that but I'm also not sure how to put it in. If this doesn't fix it should I try the method with elastic thread?
I also intend to add foam to the lower back of the leg so it joins to the foot better.
The feet are in the process of being redone to look a better with them, the originals I didn't intend to wear with legs.

Sorry I don't have a full front view...