Not at all to knock muscle building, it is important, however aerobic activity will increase lung capacity more readily, which will in turn help facilitate weight training and other toning exercises.
    It needn't be all that strenuous or involve much expense. Two steady miles at a pace of 35 minutes per 2 miles five time a week is a good starting goal. Get a decent pair of trainers and get going. In foul weather walk in an indoor shopping mall or get a walk aerobics video and do the equivalent.