LOL, I tried fishing for about a week and then moved on. I made decent money but only at night. The fishing NPC's in town will give you the quest. it is rather easy. Even though I dont fish anymore I still keep the shot quest going and just sell the shots back to the store :P.
Via night fishing a friend got full A maj heavy and a top A weapon. That's hardly a waste of time. It IS time consuming though. The only way to make fishing shots is through the sweet fluids quest but it's an easy quest and many mobs drop them. It's enough to supply me with anything i need by way of fishing.
There is a quest given by any fisherman in towns called "Quest for fishing shots" that lasts for all levels (1-80). After you take it you will see that some mobs give an item called sweet fluid. With these items, you go back to any fisherman (usually located in grocery shops) and ask him to make fishing shots. The shots you will ask to make should be the same grade as your fishing rod. Each bottle of fluid turns into a number of shots. The higher grade the shots you ask, the less you will get for every fluid.
By the way, I agree that fishing is not as rewarding as it should be. Specially on higher levels, where you would normaly expect better rewards (hardly the case). Crafting reciepes are also a problem, since they are produced only by clan halls. That means that you would have to buy most of them for a stingy price (unless you clan ownes a clan hall).
My advise would be to do the quest for the NG fishing rod and stick to low levels of fishing. Proofs of cathcing fish might be the only reward worth spending time on.
Jut FYI, you get several shots per one fluid, depending on grade of shot. And shots have their own weight. So in case you collect several thousand sweet fluids, be prepared to take few trips from fisherman to warehouse back and forth :)