Basic strength training equipment. At least you should get together a set of waist, abdomen, chest muscles, thighs and buttocks. Ordinary people practice equipment. They all pay attention to these parts.
Whether doing sit-ups or stretching after exercise, the cushion is essential. The underground is so dirty, who will lie down casually!
Dumbbell, skipping rope, weighing scale, fitness ball, water dispenser. Well, I think these are the most basic. Otherwise, the fitness ball can be cut.
Operating room. There must be a place to have a group class!
I answered according to the idea of opening the smallest gym. I don't know if it is what you want.