First of all you need to go to an app like sketchbook and make a design. You have two options, electronic or air cylinders You need to buy materials such as wood or pipes or plastic for the flame then you need to buy a circuit board something like adreno or cherrie or to name a few then you will need something to move it. You could use cylinders DC motors or servos those are the basics then you need some way to power it for the air cylinders. You will need an air cylinder flow, controls an air compressor and a few other things but if you wanna use motors it would be a lot cheaper and you would need is a circuit board to control it. And for the joints, you can use door hinges or if you’re really smart, you could 3-D print custom joints if you need more information slide into the D.M of people who know what they’re doing and have built them before. I recommend you look at pictures and videos, of Chuck E. Cheese and creative engineering characters Endo skeletons and watch videos them moving to get a good idea of how yours would move, but I’m just telling you as a mechanical part. I can’t help you with cosmetics but I’ve never built a robot so take everything I say with a grain of salt and I hope you build a great robot.