What is the most cost-effective and space-efficient way to set up a dedicated indoor training space that can accommodate a variety of training methods, including virtual training platforms, high-intensity interval training, and endurance rides, while also ensuring a comfortable and safe environment for riders of all levels, and what are the essential components that should be prioritized when designing such a space, considering factors such as lighting, ventilation, noise reduction, and equipment storage, and how can riders balance the need for a dedicated training space with the constraints of limited space and budget, and what are the benefits and drawbacks of using a dedicated room versus a multi-purpose space, such as a garage or basement, for indoor training, and how can riders optimize their indoor training space to minimize distractions and maximize training effectiveness, and what are the most common mistakes to avoid when setting up a dedicated indoor training space, and how can riders ensure that their indoor training space is adaptable to their changing training needs and goals over time.