Yeah the $50 robot is defiantly the place to start if you want to get into robotics. it is really cheap for all of the components you will need, provides a lot of room to move with chassis and mechanical deign and expansion. and on of the best things is that there is plenty of room for expansion to other platforms.
one piece of advice that i strongly recommend is to do research into suppliers and ask question of good places to go. i did and i spent way less than $50 building the $50 robot.
and read as many of the tutorials on the Sor main site as you can, admin and others have spent hour writing tutorials on all kinds of things to help new people and old people for that matter that come to the hobby. i can guarantee the more time you put in learning and reading the more you will get out of the hobby in the long run.
ask any questions you need as there are people on the forum who have been building robots for years, and there are even people who do this sort of stuff for a living and are more than happy to help. ( as long as you have had a go first!)
goodluck
Joker94
