ibis paint is a very good app, i recommend one of these pencils with rubber tips for phones, or a sonar pen if you can (those use the audio jack but are really good)
my recomendations would be to practice your lines drawing only the upper area of the body to no burn yourself in one draw.
everything depends on how much practice you have and how much patience you put in one draw.
always!
use references, with references you will develop a style and will understand how stuff work (even tracing but thats just for study purposes)
i wouldn't use bases
thats just my opinion, im not an expert or anything so, take it or leave it