While living and working abroad in the Cayman Islands, I didn't want to join a gym because it was like $55 a month. So I started doing simple body weight exercises, and I got into better shape than I ever had at Gold's. I became a big believer in the simple body weight exercises that a lot of people dismiss in favor of machines or free weights. I'll put it this way: when I used to work out at a gym, I remember trying to do some pullups once and only being able to do a few. After a while with no gym and doing not much else besides pushups, pullups, and chinups, I went to a gym with my brother and found that I was lifting as much or more weight than I ever had after months of gym exercises. Not to totally discount gyms, there are times I'd like to have access to more weights for some variety. But you can make significant gains without setting foot into a gym. I use my basement. I have no weights, just a pullup bar, some chairs for dips, a swiss ball, and the floor. If you're not in the habit of exercising, you can start now from your own home. If you're already working out, try applying some of these principles and exercises and I'll bet you'll see improvements.
First, before I share the workout plan, let's talk about two important principles to build muscle, burn more calories, and spend less time exercising: circuit training and compound exercises. They are cornerstones to building muscle in reasonable amounts of time.
Circuit training: Involves doing one exercise after another, with about 30 seconds in between at most. It keeps the workout short and and keeps your heart rate high, which gives you cardiovascular benefits in addition to muscle building, maximizing fat burn.
Compound exercises: These are exercises that use multiple joint movements (as opposed to isolation exercises, which move only one joint.) Said another way, it's getting multiple muscle groups done at once. Isolation exercises have their place, but if you don't have much time and want the most out of your exercise, compound is the way to go. These include pushups, pullups, chinups, dips, squats, bench press, and more. Notice that several of the aforementioned can be done at home with just your body weight.
Since we're focusing on workouts you can do at home, I'm going to suggest the following plan. It incorporates exercises that I've been doing personally for the past few months, but adds some exercises that make it a more complete body workout. I'm going to be doing it for the next few weeks to add some variety to my workout for a new challenge (you always want to change it up every month or so to challenge your muscles with something different so that you continue to see results.) It requires 3 days a week, for twenty minutes each time. That's it. No gym required.
I got this exercise from Men's Health. It's part of a program called belly off. Maybe it'll be worth checking out if you like this program. It's a 12 station workout. You'll need a pullup bar and a swiss ball. Do the exercises as a circuit, with 30 seconds or less rest between exercises. If you find it easy, do it again. Stick to the plan, but modify (add) if need be. For example, I will add reps in areas like pushups, chinups, and pullups, and may add dips and a few others to the mix. Here are the exercises:
1. Prisoner squats (30 reps)
2. Pushups (30 reps)
3. Jumps (10 reps)
4. Swiss-ball leg curls (10 reps)
5. Swiss-ball pikes (10 reps)
6. Stepups (20 reps)
7. Pullups or chinups (5 reps)
8. Forward lunges (30 reps)
9. Tucked-elbow pushups (20 reps)
10. Inverted rows (15 reps)
11. Prisoner squats (15 reps)
12. Chinups (5 reps)
To see a pdf with pictures and details of each exercise, click the link or copy it into your browser. (Disregard the "week 3" stuff on the pdf.) It'll give you a pdf that you can print out, so it's super easy to follow as you do it.
Try this out for a few weeks and I guarantee you'll like the results.