If you really want the cheapest way out go and buy some bulk creatine powder (mono or cee) from an online retailer. Even with shipping you will save a lot as GNC will overcharge you for less product. Places like Nutraplanet, DPSNutrition, or Trueprotein are good options.

Cardio is all about expending those extra calories and keeping the fat gain under control if your bulking. If your goal is to bulk up as fast as possible then maybe your overdoing it but it all depends on how many calories your consuming daily and ultimately how many calories your cardio sessions are burning. Get a rough calculation on both of those numbers and you will be able to adjust accordingly.