Here discuss your custom magic items and others might be able to give you tips or tricks that you could do with your items.

I started this so I could ask a question what should I do with this cursed gem, it's ability is that anyone that looks at it is charmed if they fail a unknown saving throw, and the owner has disadvantage. So I was wondering if their is anything I could do with it. 

Side note my campaign takes place during the dark ages. 

This is what the Charmed condition states:

• A charmed creature can't attack the charmer or target the charmer with harmful abilities or magical effects.
• The charmer has advantage on any ability check to interact socially with the creature

How then does that affect the creature when “the charmer” is a gem?

I’d like to add a home brewed spiked chain to my Shadar Kai to replace the whip he’s currently equipped with. Can I make that reflected in the app?

Sure, you could either add it as a custom action directly to the character sheet, or depending on the stats you want create it as a homebrewed magic item.

Thank you for the help