There is no such software to help you draw manga easily or with no skill at all, at least not free, and even those require some level of drawing skills and understanding of what you’re doing.
I would recommend to draw on real paper, at least to try, because it will train your hand and eyes better than doing it on a computer, and when you got the basic of drawing stuff, human anatomy, perspective, only then try drawing on a computer.
It will require a tablet [there are some cheap Wacom tablets, not sure about your budget].
Of course there is always the good old mouse, if you get used to it, you can draw with that too, though it will be much harder, also with the mouse you can draw in Line Art techinique, wich takes longer but the results can be amazing.
If you are passionate about some things, you better start learning them, do not use shortcuts, it’s like asking how to win the karate tournament without training in karate or at all.
- Use real paper to learn how to draw
- Inform yourself about anatomy, perspective, shapes, colors, shading, etc.
- Buy a drawing tablet to draw on the computer
- Get used to the tablet
- Try getting something done
Alternatives to the tablet [obviously this is the harder way]
- Get used drawing with a mouse
- Inform yourself about Line Art