Gamification approaches to learning use game-inspired design elements to improve learning. Given manifold design options to implement gamification in virtual environments, an important but underexplored research area is how the composition of gamification elements affects learning. To advance research in this area, we systematically identified key design elements that have shown promise in leading to positive learning results. We then conducted an experiment in which we varied gamification intensity in web-based virtual training environments for a procedural industrial task. 355 participants were divided into a baseline group without gamification, a basic, and an advanced gamification group. Analysis of participants' learning included learning outcomes (time-to-completion and number of mistakes), affective learning factors (motivation, self-efficacy, satisfaction), learning system usability and perceived cognitive load throughout the learning process. The results did not show any statistically significant difference favoring the higher levels of gamification intensity with respect to lower ones. Conversely, we found that participants' computer gaming habits and technical equipment (display size and computer pointing device) significantly influenced learning.