Buy what you want. Lots of ultra-low budget stuff to dig into. Some ESCs will be a pain to program (if at all). Some ESCs will let you recalibrate throttle settings, and some will not. Find the ESC's manual and read it. If you can't find a manual... I'd pass on it. Generally, the brushless motors are fine for what you pay. Open up the motors to find out what size bearings are used and write that info down so you have it when the time comes.