The best exercise equipment isn't always the most expensive. The key is to know your own needs and which machines can best suit them. Sure, that elliptical machine has all sorts of swanky features, but do you really need an iPod dock or a calorie counter? Shop around online first and see which features are standard. Decide which features are absolutely essential for you, and which ones are simply nice to have.
Treadmills are always a good way to start. Most people think they're just for cardio, but today's treadmills do a lot more than that. Adjust the incline and you can work out your hind leg muscles. Walk backwards and you can work a different muscle set. Carry some dumbbells and you've got the equivalent of a full body workout—all in just one machine. Choose a treadmill with safety features and a solid build to match your exercise intensity.
If you're looking for a complement to your treadmill, look into strength training machines such as bench presses. Multiple studies have shown that cardio and strength training make the best pair both for weight loss and basic fitness. Look around for models with lots of available add-ones (such as extra weights), so you can adjust the intensity as you get stronger.
Finally, don't forget to note your space requirements. Exercise equipment takes up space, and a cramped home gym isn't really conducive to exercise. Take measurements before heading out to the store, and make sure to leave enough room around each machine for traffic and installation. If you have limited space, look into portable or foldable models-they may lack some features, but they'll be more comfortable to use in the long run.