@ Lelouch
1. The best way to Level Level 50 Armors is use 4 Uncommon armors for enhancement, each set of 4 will give you one level.
2. Rares change to their last appearance at Lv 25
3. That depends on where your progress in story is at the moment.
4. 3-4 Armorsmith and all Training Fields (Don't waste your time doing building quests anymore theyre just prolonging your growth and wasting your money)