I’m currently working on a homebrew ring that I plan to use for personal reasons. But I’m not exactly sure what rarity it would be considered. I think it might be uncommon or rare, but I’m not exactly sure. 

Here are the effects. Note that I cut out a lot of fluff for this, since it would require an entire essay to give context.

You have advantage on all Stealth (Dexterity) rolls.

You are no longer affected by foul odors, including spells such as Stinking Cloud.

As an action, you can cast the spell Stinking Cloud centered on yourself. The DC for this is 8+your proficiency bonus+your Charisma modifier. Once you do this, you cannot do so again until your next Long Rest.

Requires Attunement

I would say at least Rare. This is like 3 uncommon magic items in one. 

Rare sounds fairy accurate, considering the lore behind it would make it decently common.

Let me guess the item is a kind of magical gas mask that was used by soldiers in some great war where cloudkill was used often and a bunch of powerful mages got together and mass produced this item for the magical trenches