I like your ideas with the arms and bodies, it's a tough road and it can be a lot more difficult for the self taught. Get to know your machines (there's some great online videos) and don't jump straight into tattooing friends and family.
Make sure you see your art progressing, get the theory down, learn about how to work hygienically and the dangers of tattooing and blood borne pathogens.
Learn your needle groupings and consider how you'd use them to achieve what you achieve with pencils.

Start on fruit like grapefruits or fake latex skin to get a feel for the machine. Lastly get tattooed and take it all in or visit a tattoo convention nearby, learn from watching the process, above all have integrity and realise the permanence of the job.

Good luck