As long as the robot is planned well enough, since when building a spinner there is much less room for error, I feel a spinner as a first build is completely doable. You will defiantly learn a LOT if you go through with this and future builds may be very different but there is nothing wrong with challenging yourself on a first build. I would happily bodge bits on one of my featherweight builds but never if i was building a spinner. Also as everyone else has said those drive motors wont do, drill motors are the cheap option that everyone uses or if you want even more of a challenge try getting your head around a brushless drive train. Also remember to factor in how your locking bar would fit before you start building it.