Here is a step-by-step tutorial on how to make a wire armature for around $15. This gets into how to make a puppet that will stand and walk.
Here is your shopping list:
Aluminum armature wire (from an art store or Amazon, not the hardware store)
Wing nuts (1/32)
Cotton batting or foam
Aluminum foil or wood ball (something for the head)
Wipes (Epoxy putty gets messy)
taught this process at the Academy of Art, and if there is one
consistency, it is that when students are cheap with the materials or
stray from the process, things go wrong. A challenge with stop motion
animation is to hold to your vision while working within the physical
limitations of tight-budgeted productions. Compromise is always
necessary. The goal is to make a puppet that is easy to use while
animating so your attention can go towards the performance and not the
struggle against gravity.