Very good resource on building robots, great for beginners to start with. The total cost its under 200 $ and the building time around 2 hours. The electronics used are ”real parts” (not little homemade things that wont really work unless you spend hours of tweaking, and not a kit that you just assemble and that´s it). You can evolve from here, even with the same parts (if you can bare to take your robot apart).
Build a robot step by step instructions: