Purchasing your first trout flyrod should not be an arduous task. There are many graphite and graphite composite rods on the market in the $100 price range, that will more than satisfy the beginner.
HERE ARE A FEW POINTERS TO HELP YOU OUT:
The first thing to remember is that the rod weight is specifically fitted to the line weight. Line weights will range from 1 thru 16, 1 being the smallest and 16 the largest. Line weight refers not only to the diameter of the line, but to the actual "line weight". The weight of the line being cast foward or backwards, will create enouhg resistance to flex, or "load" the rod. The correct weight flyline for the will load the rod enough to give distance to your cast and also the needed delicacy to the presentation of your flies.
Second, you must ask yourself, "What types of streams will I primarily be fishing on?" This will help to guide you as to the the rod length most suited to your needs.
Generally, 7'-8' rods are best suited for small creeks, brooks and mountain streams with tree and bush cover. Most of these rods are in the 4,5,6wt. class. They are fine for casting small dry flies up to medium streamers. A nice bonus with smaller weight rods is that smaller fish feel like giants.
The 8 1/2' to 9 1/2' rods can range anywhere from a 2wt. to 10wt. but most are in the 5,6,7wt. class. They are better suited to longer casts, bigger fish and bigger water like those found out west. They will handle larger, more wind resistant dry flies, wet flies, streamers and weighted nymphs.
For your first outfit I would suggest a 2 piece rod. The 3, 4, and 5 piece travel rods are nice to carry,however the extra ferrels these rods contain tend to add weight to the rod and could hinder the rods action. The action refers to the distribution of it's ability to flex. A fast action rod will flex about 1/3 of the way down the rod from the tip to the butt. A medium action rod will flex about 1/2 way down and a slow rod about 3/4 of the way to the butt. For a basic trout outfit fast to medium action is preferred, but a beginner may find a medium to slow action rod easier to learn on. These rods will give you more power and help you to learn "timing"(see basic casting).
The most important thing to remember is that this will be " your" flyrod! So have some fun, head down to the local tackle shop and take a few practice casts with rods of different weights, lengths and manufacturers. Before you lay down your hard earned dollars to buy it ask yourself, "Is this the one that feels most comfortable? Does it feel like an extension of my arm? Can you see yourself battling your "fish of a lifetime" on it?" If your not sure to the answer to these questions ask for help, I'm sure the store owner will be more than happy to give you all that you'll need. A few well placed questions could save you time and money in the longrun.
HAVE FUN AND GOOD FISHING!