Since it's not on the store page, and I don't feel like leaving a review just to explain what's in the bundle. The bundle contains nine Amplifications, which you will have at the start of the game. These all have a blue diamond and have a description indicating that they are rare.

Miracle Liberation
Gamers' Mania
Galaxy Sound
Factor Analysis
Reincarnation
Breaking Rules
Third Echoes
Governing Ruler
μ-tation Record

Also Steam has pictures of the Casual Clothing Bundle here. I don't know why GOG sells this bundle but doesn't have pictures, except to say that they're actually a lot worse than I thought they would be.

Steam only sells the swimsuits individually, not as a bundle, but they actually manage to be worse thus I'm not giving links for all of them. For example, here's Eiji's swimsuit.