My advice:
If you are on a budget Harbor Freight 18 Volt Drill Motors are great. I use 4 of them in my bot and I consistently finish in the top 3. (You can get them here
http://kitbots.com/product.sc;jsessionid=D9D840EBCBDC4C577C1F2C842FFDD1B0.qscstrfrnt06?productId=6&categoryId=1 for $25)
Colson Caster Wheels are good and these hubs allow easy mounting of a Colson Caster Wheel to a harbor freight or drill motor
http://kitbots.com/product.sc;jsessionid=D9D840EBCBDC4C577C1F2C842FFDD1B0.qscstrfrnt06?productId=5&categoryId=1If you don't want to work with metal UHMW Plastic and Lexan Glass are great. Lexan glass is the same stuff used in arenas to contain bots when they fight. UHMW is virtually unbreakable.
For a scoop or wedge 4130 steel or 6ALV Titanium are good. They are both very strong materials. My bots new lifting spike is 6ALV Titanium.
For a metal frame 2024, 6160 or 7075 grade aluminum are all good. 6061 is about 1/2 as strong as 7075.
If you want or need CAD software you can get it at
http://students.autodesk.com if you are under 18 and have a E-mail that ends in a .edu
Good luck