Building robots can be difficult, and if you want to construct something humanoid, designing the mechanics alone can be a significant task. ASPIR, which stands just over four feet tall, looks like a great place to start.
John Choi’s 3D-printed robot can move its arms, legs, and head via 33 servo motors, all controlled by an Arduino Mega, along with a servo shield.
The documentation found here is excellent; however, it comes with a warning that this is a very advanced project, taking several months to build along with $2,500 in parts. Even if you’re not willing to make that commitment, it’s worth checking out for inspiration, perhaps parts of the ASPIR could be adapted to your own design!