After buying a treadmill, 1 month, it basically became a decoration. Unless you have enough motivation and will.

At least have friends and coaches to urge and maintain your motivation to continue exercising.

In short, if it's a whim, go to the gym. If you make up your mind, buy a treadmill or simply run outdoors, and then use dumbbells, horizontal bars, parallel bars, abdominal wheels and other training is enough.