Use your workout equipment in an order to see maximum results. The order should be dumbbells first, regular barbells second and machines last. Doing exercises in this order will ensure that you don't get fatigued too early in your workout, by engaging in the more labor-intensive equipment first. This also works your muscles out, from smaller to larger.
Check out hiring a personal trainer to help you with your workouts. A trainer can push you past the walls you have set up for yourself, sending you down a path of new and better workouts. A trainer is incredibly helpful in helping you determine the right exercises for your goals. If the price is a barrier, try signing up for small group training sessions.