Definitely hard to tell without seeing the bike, but if it was me I would check the easiest things first. Have you tried jump starting it or push starting it? When you hit the starter does the engine try to turn over at all or do you just hear the noise of the starter? If the engine is not turning over at all then I would think something electrical. Battery, starter, switch (kickstand switch, clutch switch etc). If it is trying to turnover but not starting, then I would check the battery and carburetor.
I honestly work on cars and my ninja is my first bike. Its never given me any problems, and other than an oil change Ive never had to do anything to it. Just telling you the things I would check. Good luck bro.