All items to buy in the shop should be social in nature. If your use/existence of the item doesn't affect other members, then you should just have the item as a default feature.

Buy stickies of varying strength
Buy message icons
Buy profile backgrounds to fill in the blue space
Buy profile themes that give the entire profile a custom feel
Buy bulk likes/super like. Has ten times the power of a regular like.
Buy change custom title
Buy change someone else's title
Buy steal credits
Buy mod immunity (joke product at super expense)

Credits
KASS
1 credit per wall comment, 2 credits per post, and 3 credits per topic. A wall comment like gives you 1 credit. A post like gives you 2. A topic like gives you 3. Someone liking your profile gives you 5 credits.

Topics give the OP bonus credits upon reaching milestones. Every 10 responses gives 2 credits, up to 500 responses.  Thus a total of 100 bonus credits can be earned from topics.

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