Highlighted weapons are free options.
Jean's Skill can be used to fling smaller mobs into the air to deal fall damage, and to stagger bigger ones. Her healing scales with ATK.
While typically Jean will heal enough that you do not need to try and build for as much healing as possible, when paired with Furina it can be beneficial swapping to an ATK% goblet and Healing Bonus circlet. This is to aid in building Fanfare points faster, and Jean's personal damage is not particularly significant to begin with. When building Jean in such a way, prioritize weapons which provide ATK% or Energy Recharge. If using , a CRIT Rate circlet can be taken to ensure more consistent procs.
For Support Jean, you can either go for more ATK for stronger heals, but relatively lower Burst uptime, or more Energy Recharge for lower heals, but higher Burst uptime. Choosing between these two is up to personal preference, although if another Anemo character is on the team, Jean has very few energy problems and can potentially go for a full Sub DPS build.
If you prefer more damage than healing, prioritize Skill over Burst since it scales better.