The world distance records for women and masters were set with 150g or lighter discs and the overall world distance record was set with a 169g disc. That said, if you can generate the same arm speed with a heavier disc, it will go farther because it has more momentum. Also, most players are more accurate with a heavier disc. The second guideline is to start with a stable or an understable disc. I'm a huge fan of the stratus, stingray, comet, and shark as beginner discs.
Lightning also makes some extremely user-friendly discs that are good for beginners.
You should concentrate on releasing cleanly and keeping the nose of the disc down. If you get the nose up your disc will stall out and fall off to the left, costing you distance and accuracy. For More Information John Houck has a video called Learn to Play Disc Golf which does a good job of covering the basics, there are also articles in many issues of Disc Golf World News with suggestions to improve your throwing technique. Probably the best source of information, though, are the good players around your home course. Watch them and talk to them, ask if you can play a round with them, most of the time they will say yes.