How to get the most out of the memory on my computer?

So I started downloading my favorite TV shows on my computer (me + my 2yr old son). I can't really afford an expansion on my Mac's memory and instead of cable I watch a lot of my favorite TV shows online but my landlord's internet is not dependable now. My son watches his shows on his ipad and our flat screen (through my computer)

My computer finally told me the 'macintosh MD startup disk is full' and I love itunes ability to organize my files for me especially the tv shows. Any recommendations to handle my computers memory? I was thinking of.

A- Move all the movies to an external hard drive.iTunes has a media folder designation and although I know i can change it i don't know if i can separate movies/tv shows to external and keep music on the computer.

B- Delete some of my old files. I known I have to go through them but they are mostly word doc from college since I don't take pictures and stuff. Also since Itunes makes copies I delete everything except movies original files in.avi (I use a convertor program to change.xxx to.mp4 for iphone. I figured some conversions will change the pixilation and impossible to return quality if converted bac)

C- Use something other than itunes. I have an iphone and I been taking advantage of the mac-iphone-ipad bond since day 1

Any recommendations are truly appreciated. I'm not really tech savvy.

Easiest and cheapest way is to A buy an external hard drive no smaller that 250GB - 320GB.

once brught you connect it to your mac then you can control what goes on there by dragging and droping, copy paste etc.

This is the best for you.

All te best