It depends on the goals. Building strength (without looking like Dwayne Johnson), cardio training, weight loss? I would bet on Kettlebell training.
You can train whenever you want because you can store even a complete Kettlebell set (which you don't need necessarily depending on your starting strength) in your apartment easily. You'll find a ton of Kettlebell exercises at YouTube. Having said that, I'd recommend a basic instructional course first. You better have someone at the very start that can control your posture while doing exercises like Swings - your back will thank you. Maybe you'll find a CrossFit trainer in your gym that can instruct you.
I tried that too


I mean, its ok, just ok. Not the same for me. I do realize that you can achieve good results with these but I simply don't have the exponential motivation to train solo with a computer screen (eventho it's a genuine time saver!).
So 4 years ago, I immersed myself in a gym environment and it worked for me. I needed to be surrounded by multiple challenges and other desperate souls! lol I achieved my goals, firm butt and toned body. So I'm not letting go! I mean, in the end, whatever works for you, right? That's what my sis does, crossfit. But she's in there all freakin' day! I've got a professional life! lmaoo