Your proposal is leaving many important questions unanswered. I'll list here the most important ones:
- Does the motor have enough torque to move the user standing on the longboard? If so, what was the estimated payload you used to choose the motor? If you haven't estimated the torque then most likely your motor does not have enough torque (in which case it will catch fire on the first try) or it will have too much torque (in which case the user will lose control on the first try).
- Is the battery's maximum amperage consistent with the choice of motor? Even if you properly designed the motor, the battert might catch fire if you are trying to get too much current out of it.
- How many meters do you estimate the longboard to move in a single charge?
- How are you going to recharge the battery?
- What is the Drive Train? Are you sure it will cost $50?
You need to put more work in your proposal. Please meet with your TA to discuss these issues and update your proposal as soon as possible. Until you haven't figured out the correct battery/motor combination you cannot purchase any of the other parts (you might have to dramatically change your design).