Board Thread:Questions and Answers/@comment-91.121.132.228-20150919072554/@comment-26097716-20150921142343

If you want to, you could actually try stock up resources while doing quests, and clear 6-1 and moving on to 6-2. 6-2 drops Shoukaku and Nagato frequently but be warned, it's a pretty expensive map to run continuously.

Normal constructions are just a waste of resources.