Started working out, but only lifting weights once a week. (but walk 3-4x a week.) am i wasting time with weights-stretching my muscles for nothing?

No!: Exercise is never a waste, no matter how little you do. Something is better than nothing. Remember that you have to lay a foundation in order to build a skyscraper. Likewise, w/exercise, you start slow & gradually increase your strength, aerobic capacity & flexibility. It's important that you practice proper technique & push yourself regularly to improve & get better. Gym membership not required.