So you want to build your own robot spider? The XYZRobot-Bolide Crawler kit has you covered. It lets you use your XYZrobot Bolide‘s 18 A1-16 Smart Servos to get started. You can control your robot from your iOS or Android device. You get 3 servos on each leg, so the crawler can walk on uneven surfaces.
This robot is compatible with Arduino. You can create custom movements for it. The upgrade kit is available here.