The following page of the Disgaea RPG guide contains information about the in-game paid content. We suggest which things are best to buy for real money.
In the Rosen Queen store, you can buy Paid Nether Quartz. Thanks to it, you will get better characters in the Summon tab when rolling paid banners.
The Item Pack contains packs of the most necessary items. If you buy the Daily Pack, you will get 50 Free Nether Quartz, 50 Paid Nether Quartz, and 5 coupons for Dark Gates and Events. Buying Daily Pack each day will get you more coupons per month than you would get from a Weekly Pack or a Monthly Pack.
Skip Coupons are the most useful, especially those used in Dark Gates. You buy these coupons for HL coins, but there is a daily limit. You also occasionally get them as rewards for completing tasks. If you decide to visit Dark Gates every day, which we recommend doing, you will see how useful Skip Coupons can be.