“Basically I want low body fat and relatively high muscle mass”
This is probably the most common question I hear--it’s basically going to come down to compound movements and caloric intake.
Compound movements like bench press, overhead press, squat, and deadlift are going to be your best friends on any kind of weight lifting program. This is because they work multiple muscle groups at once, versus isolation exercises like bicep curls, tricep extensions, and leg extensions--exercises that work exclusively one target muscle group. These compound exercises are going to be both the most physically taxing, which will help burning calories, and also save time, as they work multiple muscles at once.
You also don’t need to stress too much about rep ranges. Similar levels of hypertrophy (muscle tissue growth) and strength occur with weights anywhere from 30% to 85% of your 1 Rep Max (1RM). This means that, using my squat as an example, I will gain similar levels of progress using anywhere from 106 pounds all the way to 300 pounds. Heavier loads will result in bigger strength gains but, for the most part, as long as the intensity of the workout remains the same, so will the progress.
When I say “intensity”, I mean a subjective scale of how hard you’re working--Rating of Perceived Exertion, or RPE, a scale from 1-10 of how much effort you’re putting into your sets.
The optimal RPE for growth is 7-8. Meaning that, contrary to popular belief, you shouldn’t lift weights until you can’t lift them anymore--you should finish your sets feeling like you worked about 80% as hard as you could, with 100% being absolute failure.
I highly recommend picking a novice lifting routine like StrongLifts 5x5 or Fierce Five and sticking with it--you’ll see impressive progress, as long as you follow the program closely.
As for maintaining lower body fat, that comes down to calories. Check out the previous post about losing fat while gaining muscle--that should answer your questions on what your diet should look like. There’s no reason to deprive yourself of fun foods--it’s not necessary at all.