I have a D5300 and I am also a beginner, but I have been doing speed ramping without a problem. I am not an expert but I think if you want to do a shot similar to 120fps, then shoot slower in 50fps, if my math is right, shoot 1 second of shot in roughly 2.4 seconds. All you have to do is plan the shot, test it a few times and you'll be good to go. Don't really worry about motion blur because when u speed ramp it, it won't really matter as much as you think it would. So if 217% works for the type of shot then go for it. Practice it daily. I recently shot a practice video testing speed ramping: http://y2u.be/wHdUdoHhzko Sorry if link is not generated, using my phone to reply. Any feedback is appreciated! I will be doing a 24fps microfilm soon! Hope it helps! Don't give up.