@robbybedfart:
Luffy learned Soru, gear 2 and gear 3 off camera. It's not Oda's style to show a training arc, just the implication he's about to train. A panel or two of "I need to get better", followed later by the results, will be enough. Ditto for ALL the strawhats, who are getting off camera training arcs at this very moment.
How Luffy learned gear 2 was screen in one of the movies. It was the movie, who he fight against a big mecha robot. During this fight, something heavy drop on his head and activated his gear 2 effeckt. Becoming fast and nobody understood, what happened.
Later in manga and anime, he speak only, he wanted to try somethning and activated gear 2 on his own by forcing his muscle to simulat the impact of something heavy.
Gear 3… is in my eyes only a different form of his ballon technic, but far more advanced