I will have to agree with big_ness in regards to high intensity workouts reaching greater results. It is not about how much time you spend at the gym but the intensity you bring to your workouts. Sometimes my workouts last no more than 7 minutes but those 7 minutes are filled with a lot of intensity. I have seen incredible results from myself as well as the members at my gym.
I will give you an example about my personal experience with intensity:
Unlike most people, I love the treadmill and love running long distances. It is a good way to keep me lean and stress free but it wasn't helping me with my speed, strength, agility, etc. I was able to complete a marathon but in the end of the day I was weak. My muscles were not balanced and I got injured a lot.
I eventually learned about intensity with interval training. Instead of just running for an hour, two or three straight I incorporated sprints. As an example: I sprinted for 1 minute, I jogged 3. That significantly reduced my workout to 20mins and my legs got stronger, I got faster, I got way leaner, my muscles were balanced.
That was just an example of what intensity can do for you: decreases workout time, increases results. I won't lie, running 3 hours straight is easier than a 7minute intense workout. But the results are worth it all.
I am not informed of your fitness "level" but, speaking for myself, I keep 3 things in mind when it comes to my fitness and health:
Feed your body what it needs in order to give you the energy you require to finish the work. Workout and make sure you are serious about it. Lifting something easy is just a waste of your time, push yourself (but be safe - know your limit). Rest - give yourself plenty of sleep, take some days off.
I should also mention the fourth thing I consider: TIME.
Be patient about it, your results will come as long as you don't waste time and do the work with no excuses. There is no better time than the present.
Don't be afraid to explore your gym. The gym should be seen as a friendly friend not an enemy. SO have fun with it!!!
I am a huge advocate about free weights vs machines. That will help you much better in the long run.
Fact: muscle burns fat.
Use your body weight. After all you do carry yourself everywhere you go. Do pushups, burpees, air squats, run, jump rope, do jumping jacks, jump boxes (or plates if a box is too high), etc.
Don't be afraid to modify your workout. If you cant to regular pushups then do pushups with your knees on the floor. If that is challenging then do pushups off the wall. We all start out somewhere, don't be ashamed of that.
Lastly, I ranted long enough, I suggest doing more multi-joint workouts or as I like to call it "functional movements" instead of isolated workouts. Bicep curl is an isolated workout, pullups are multi-jointed.