E.O.S is Electro-Optical System, and also the Ancient Greek goddess of the dawn.Your Canon Rebel G has an EOS lense, I don't know the exact acronym but it stands for something like Electronic Optical Stabilizationg (or whatever).
The older Cannon FD mounts are nice but the prices are going up. They are also dead-ends. The EOS lenses have the option/capability of being mounted on digital camera bodies should you wish to pull double duty later on.
I would definitely stick with what you have for now. Just do it all manually (don't let it focus, don't let it set aperature, shutter, etc... Just use it for a light meter and take your own shots). Same result, and you don't fork over a ton of money.
I found that my standard 50mm prime wasn't doing justice for group photos and interior house shots so I got a wide angle lense. 28mm for me, but anything 35mm or so is decent. On top of that I have a minimal zoom (around 70mm-200mm) which is very useful for things slightly further away. I don't always zoom to the max, but it gives you that option to frame your shots better than a prime lens does.
Just general shooting, I would say you should have everything covered with 2 lenses:
1) 28mm (or 35mm) to 70mm (or 80-100mm, whatever) <-- your main shooting lens, from wide to just a bit closer than standard.
2) 70mm-80mm to anywhere in the 150mm or 250mm range. 300mm and up get really pricey.
#2 is optional. Can be bought later. You can get it all done with a prime lense (50mm/f1.4) but having that ability to zoom is more useful for framing of shots.