Candace is a 4-star Hydro Support who specializes in providing off-field Hydro application with her HP-scaling Burst, infusing melee allies' Normal Attacks with Hydro and providing defensive utility with her Skill.
It is worth noting that Candace will never be the strongest option for your teams. At the cost of having different kinds of utility in one kit, she will never be the best at them. Her damage contribution is surpassed by offensive Hydro supports like Xingqiu, and her defensive capabilities are outclassed by other Hydro healers.
Because of this, it is recommended to focus on Candace's strength as a consistent Hydro applier by getting as much Energy Recharge as possible, helping her maintain consistent Burst uptime. Her weapon and artifact rankings therefore focus on Particle/Energy generation and Recharge.
In some teams, Candace's hold Skill cooldown is too long for rotations to work properly. If Candace is not C4, avoid getting hit and use a tap Skill as quickly as possible.
Regarding Weapon Choices:
Favonius Lance: This is Candace's best option because of her drastically high Energy Recharge requirement. If she is the only Hydro character on the team, she will need nearly 300% Energy Recharge to maintain consistent Burst uptime. With another Hydro character, this requirement drops to around 200-250% Energy Recharge. This kind of requirement is difficult to reach with most weapons, but each passive proc cuts this requirement down by about 20%.
Staff of Homa: Can be considered if you want Candace to have high personal damage, which is usually notable at C6.
Deathmatch: Can be considered if you want Candace to have high personal damage, which is usually notable at C6.
"The Catch": Candace's strongest F2P option thanks to its high Energy Recharge and Burst-enhancing passive.
Regarding Artifact Choices:
Sets
Scroll of the Hero of Cinder City (4): Even though Candace is not from Natlan, she can still take advantage of the 12% DMG Bonus buff for the team, alongside the Flat Energy refund from (2) if there is a Nightsoul Burst being activated on the team.
Emblem of Severed Fate (4): The only necessary artifact stat for Candace is the 20% Energy Recharge from the 2-piece effect. The 4-piece effect lets her better capitalize on the high Energy Recharge amounts she wants to equip, making it her strongest personal option. However, is a highly contested artifact set and thus it is possible for you to end up using the 2-piece + 2-piece alternatives listed above.
Substats
CRIT Rate: Only recommended if using a Favonius weapon.