Since you don't want to lose weight, do more muscle training instead of cardio. Some women are afraid of trying weights because they don't want to bulk up but that's not true. Doing less reps more weight will build muscle, doing more reps less weight will tone muscle. If you just want to tighten, elongate, and strengthen your muscles, then go for the second option.
There are plenty of Youtube videos online with bodyweight exercises you can do at home with no equipment necessary. If you have dumbells (or you can use two water bottles or tin cans of food) you can work out your arms. You'll be surprised how much stuff there is online and how you can get fit in the comfort of your own home w/o spending $ at the gym. Some good channels to start off with are XHit, Blogilates, FitnessBlender, and PopSugar. Remember to change up your exercises so your body keeps guessing. And although you'll be doing mostly muscle toning, don't neglect to do a little bit of cardio and ALWAYS stretch after your workout.