Build a model. Car, plane, tank, ship, figures.
Yea, being a 70's kid, getting a model to make as a gift was just the greatest thing. My older brothers had an entire cabinet dedicated to finished models - mostly military themed. Spent hundreds of hours playing with them after putting them together, painting, putting on decals etc.
Hobby lobby has 40% off sales, which is a start. It's a good hobby, not space intrusive, no huge outlay to start, and any interest is covered. Mechanics, dinosaurs, star wars, Planes, science, armor, etc. Try spruebrothers for a look around.
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