The easiest way is complete the High Difficulty missions. The challenge missions on the last tab of the missions menu. Aside from that I think the most recent free missions com Megaton Difficulty too.
@@AznabelGaiusDingirLu I was able to get all the parts for Mazinger and Getter 1 but now I'm tryna figure out where to farm the components so I can learn getter beam/breastfire and rocket punch/getter tomahawk. Were you able to unlock those moves?