This is a great start. When i need to figure out perspective on a drawing like this, i always try to find the joints and feet in perspective first and build a box using those points to make sure i have a good scaffolding to build the forms on. Establish the foot pads on the ground plane first, so when you have to move the limb forward or backward, you have something to compare it with. Once you have this reference established its a lot easer to build the forms over it. Hope this helps.