Иансан's buff is based on 3 Factors:
Иансан can hold a max of 54 Очко Ночного духа, and her buff decreases in value when she's below 42 Очко Ночного духа. Consistent movement is needed to maintain good buff uptime.
Иансан's [C4] allows her to frontload Очко Ночного духа if it had ever overflowed previously.
Иансан buffs her teammates through her Взрыв стихии, as well as provide some additional healing for the active character through one of her passives. Characters with movement-based abilities will greatly contribute to Иансан's buff as Иансан's own movement cannot contribute to it. Movement is needed to help Иансан maintain a high number of Очко Ночного духа, and the active character gaining and consuming Очко Ночного духа can also contribute.
Movement is defined as anything that moves the active character for any amount of distance, whether vertical or horizontal. This includes things such as attacks, Элементальный навык and Взрыв стихии animations, jumping, etc. Almost any kind of movement will contribute, as long as it's not Иансан's own. This also extends to the gain and consumption of Очко Ночного духа.
Иансан's [C1] gives her 15 Energy upon consuming 6 Очко Ночного духа as long as she's in combat and in Благословение Ночного духа state, effectively changing her Взрыв стихии cost from 70 to 55. This has a cooldown of 18 seconds.
It is important to note that at [C0], using non-Восстановление энергии weapons in teams where Иансан is the only Электро may be unrealistic due to how high her Восстановление энергии needs can become. In addition, in teams where movement is scarce, ATK weapons gain greater value.