So, first things first, study the available robotic platforms, Khepera and e-Puck and determine what are the desired goals and then define specifications.

Khepera Specs are awesome, looking at the latest Khepera IV variant, small in size, camera, IR and sonar sensors, encoders, arm extension, RGB lights on top and simulation in V-Rep and WeBots and other software - COST is about 3500USD if I remember correctly.

I wanted to make a robot within 350USD - the bare material costs, software costs not counted for.

Minimum Robot Specifications

• IR/Sonar sensor skirt around the bot
• Round/Circular design
• Differential Drive
• IMU (Gyro + Accelerometer) + Compass Sensor
• Wireless Communication
• Encoders
• Re-Chargeable Battery