Magic Items

The World of Avatar is debatable with regards to magical items. Potions also fall under this category.

For

 * When wearing Kyoshi's garb, this assisted Aang in triggering an 'image' of Kyoshi, suggesting the items were linked to her spiritually, or magically.
 * Furthering this, in one particular, short lived Avatar game, items from past Avatars could be collected to give a bonus to the player character, pushing the notion that there are spiritual items, though this game is not canon.
 * In the 'Legend of Korra' game, which is arguably canon, the in-game shop has magical items, such as the 'Shadow Fist', though this is a weak argument.
 * The Ruby Monkey Idol, which both Katara and Iroh become fixated on, is possibly a magical item because of the way it acts with people.
 * The Spirit Oasis Water Katara receives from the Northern Water Tribe has 'special healing properties': what exactly this implies is speculative, but it seems to 'resurrect' Aang.
 * Korra says, after having tea brewed by Iroh in Wan's Teapot, that she can still taste a little light in it, implying that the teapot is in some way spiritually imbued.
 * Varrick's discovery of spirit vine energy draws into question how exactly spiritual objects work, but leads to the conclusion that other objects could be spiritually charged.

Against

 * Bryke supposedly intended specifically for there to be no magical items, unlike other fantasy franchises, to avoid power-creep.
 * There is no concrete evidence in lore that there are magical items, at least, no indisputable evidence.
 * There is no evidence of potions, in a traditional fantasy sense. Aang once has the 'chi enhancing tea', but this is not a potion, and suggests that all concoctions are non-magical and simply biological enhancers.
 * Further, there is no evidence that alchemy was a concept in Avatar, as a precursor to science.
 * Adding magical items would add unnecessary complication to what is otherwise a simple system.

Conclusion
There is some evidence for some spiritual items, but it is loose evidence, which I think leaves it down to interpretation mostly, but for the sake of remaining lore friendly, no new magical or spiritual items should be added, in my opinion.

Wan's Teapot
Spiritually imbued item When used to make tea, it is noticeably delectable and tastes 'like light', ever so slightly; this grants you +1 constitution for 12 hours.

Spirit Oasis Water
Vial When used in coalition with a Waterbender's healing, this can resurrect characters who have died within five minutes of death, when applied to the wound that lead to their demise; this leaves the newly resurrected character unconscious for 1d6 x [their total HP] days. Alternatively, it can be used to heal any wound, removing all signs that it was ever received, and healing to full HP; relieve extreme psychological trauma, or madness, or; be consumed like regular water in times of adversity.