To make Chapter 6 or later required Combat Scope Betas cost 3,000 Gold, one glass shard, and one scrap of iron. The wandering merchant sells glass shards and iron scraps for 200 and 150 Gold respectively. Combat Scope Betas sell for 4,100 which means there is a profit of 750 per scope multiplied by 999 which is 749,250. The best time to perform this is chapter 6-7 just before the merchant starts wondering why she is always at the Waterless Bridge. In chapter 8 plus, she can be at Forsaken, the Waterless Bridge, or the Righteous Tower. Your best bet then is to get into an enemy counter, run away, and check the location to see if she is there. Time phase changes also change her position. Keep repeating until you have the desired amount of money.
When you have completed the game you will be able to start another session on your saved game file. In the new session when you reach Chapter 2 you can enter ReanBell's (Leanne's) bedroom and press 'Action' at her wardrobe to enable a secret button which will allow Reanbell to remain in her current costume instead of changing into the pig T-shirt in the cinematic.
During or after Chapter 7, select Leanne and look at the wardrobe in her room. When she says 'Hmm, I think that outfit is in here...' enter one of the following codes and press A to advance to the next line of dialogue and unlock the corresponding costume.
Unlock Politan Suit: Click Right Analog-stick(3), press Right, Left, Y, X, LT, RT, LB (earn the Reindeer Suit in Neverland first).