Certainly most people could do with some weight training. This is the bare minimum, but training with real weights is also really valuable (Barbells and the like).
6 months of 3 day per week training will leave you with more muscle than the vast majority of people and leave you in good muscular condition for years (even if you stop training afterwards). Even that might be more than most are willing to dedicate to it, but if you've been thinking about going to the gym at all then know it's well worth it. You'll look and feel better for it :)