O.K. Your D50 is a marvelous little machine! I love mine. Good information, here! First, do you have your D50 manual? If so, read it, underline it, tab it...keep it under your pillow. Next, go to Kenrockwell.com, and read his practical Nikon D50 user's information.
So, you have Auto down pat,and want to progress? Great! The D50 is designed to do a lot of the hard stuff for you, And I also strongly recommendbut the purchase and reading of Bryan Peterson's book, "Understanding Exposure" 3rd edition. That book contains all you will ever need to know about exposure!
Next,if the poor camera's mode dial isn't stuck on "AUTO" set your camera to P, which is "Program",or "Pro" , or "Panic" mode. This will allow a bit more manipulation of shutter speeds and aperture.
Learn where your ISO button is, and use it judiciously. As mentioned, learn the interrelationship between the three sides of the exposure triangle...ISO, Aperture, and Shutter Speed. That's the foundation of the whole thing!
Then, when you think you have it figured out...shoot, evaluate, adjust, repeat. Carry a notebook. Write down what you like, or what didn't work,so you won't forget.
Photography is a Magical art! ENJOY the journey! Don't get too bogged down in the mechanics...gigaframmises, bunabs, Bokeh...(sort of sounds like a cat hacking up a hairball, doesn't it?) or whatever. One old- timey photographer said something like...the mechanics of photography can be successfully taught in an hour...(probably 3 for me) It is the eye, and that takes a lifetime to develop. Good journey!