Whether you need to accumulate equipment over time, or money is not a concern, you can make a nice home gym on just about any budget. In my opinion, this list of equipment is a must:
TRX Suspension Trainer
This is where I would start. You can get the most versatility out of this “gym in a bag”. You can work your pulling movements, pushing movements, squats or lunges, and work your hips and core with this. You just need a good place to anchor it to. You can get away with using the door anchor that comes with it, but as you get more advanced, you will need to have it anchored where you can be directly under the attachment, or go beyond the attachment point. In my house, my basement is unfinished, so I use an I-beam.
You pretty much need some form of external load to use with your exercises, so you need these. These are pricey, but think about how much money and space you save if you buy these instead of several pairs of dumbbells. Regular dumbbells are at least $1.00 per pound. If you are a woman, you can probably get away with buying a pair that go up to 40 lbs. per hand. If you are more advanced, buy a set that can go heavier. If you are a man, you can start with a 50 lb. set, and then buy expansion kits that can make them go to 70, 90, and even 125 lbs. per hand.
You need a bench. It should adjust from flat to a few different angles for incline. You don’t need to get a commercial grade bench; it’s just going to be you using it so you won’t have to worry about meathead kids tearing it up doing stupid stuff. Just make sure it can handle a decent load. I’ve seen benches with stickers on them saying they could only handle 250 lbs., I weigh 200 lbs., so I could only use 50 lbs. when laying on it!?! I think that company is trying to keep you weak. I personally use the bench PowerBlock makes, it gets the job done and can hold 550 lbs. You’ll be able to do a variety of pushing, pulling, single leg squat variations, and hip thrusts with a bench.
Same reason as having adjustable dumbbells, you’ll save money and space if you have one of these. Regular kettlebells average $1.50 to $2.00 per pound when you buy them. Exercises that you need a kettlebell for are swings, goblet squats, and Turkish Get-Ups just to name a few.
These are a great modality for power development, and very versatile. If you have a concrete wall to throw against, you can do chest passes and rotational throws, or just use a partner. You can also slam them on the ground.
Adjustable Plyometric Box
For people more advanced, you can use a plyometric box for box jumps, single leg hops, and depth jumps. Just about anyone can use a box for step-ups. You’ll want something that at least goes as high as your knee.
If a cable machine is out of your budget, you can use resistance bands to do most of the exercises you would do with cables. These are also portable, so you can take them with you on business trips and vacation to get in your workouts.
You don’t have to buy the official “val slide” that was marked up because it’s fitness equipment. Just buy the set of 4 sliders at your local hardware store for $8. You can work your legs and core very well with sliders, and just like the resistance bands, they’re portable to take on your trips.