The fastest way to fail at a DIY humanoid robot is to start with walking legs. Biped locomotion needs expensive actuators, balance control and mechanical stiffness that most hobby builds do not have. A useful first humanoid keeps the human-facing form but uses a stable wheeled base.
Build the robot in layers: mobile base, torso, head, arms, then perception and voice. The first milestone is not walking; it is a robot that can roll around, turn its head toward a person, gesture with arms and answer commands without falling over.