I got my first e-cig (the eGo) few days ago. The kit came with 5 pre-filled cartridges.  I thought the cartridge would last me about 100 vapors as advertised but it seemed less than that (I am not going to bother measure it.) Anyways, it's time to buy refills and I'm lost in the site of what exactly do I need?

So far it seems like if I get an eJuice , I can drop some in the cartridge to make it last longer when it slows down... so I do I just get more prefills and ejuice? About about the injector and empty cartridges or is that just for the eGo-T and not an option for me??

Since your a newbie with the eGo setup... I would recommend going with some dual coil cartomizers.  They screw onto your ego battery and fit perfectly.  These dual cartomizers allow you to drop anywhere from 20 to 30 drops of ejuice into the carto - then it will lasts along time.  These cartomizers are disposable - but will lats you anywhere from 3 days to 10 days - depending on your vaping.  You will also need to get some juice - get some with a VG and PG mix.  I like American eliquid store.  You can buy the dual coil cartomizers for about $3 each at Smoktek.  probably best to start out with about five of them.   You will like the way these vape and convenient to use.  Good luck........