Gym planning?

Do you have a plan for your gym workouts? I've been going 3 days a week (about 50min sessions) but with no real aim and I feel like I need to make a plan but don't know where to start 🙈 I want to lose weight and tone around my tummy, thighs and upper arms. I can't freelift weights due to back problems but I can use machines and I know my limits on those.