Below is a list of skills that is used by healers. You don't have to slot them all, you have to experiment and find out on your own at first. I recomend you to start out with Healing Springs + Rapid Regeneration/ Mutagen.

Rest staff:
*Healing Springs (mandatory area heal)
*Rapid Regeneration/ Mutagen (either morph is good, and good to always keep up those HoTs in case you get locked, cc'ed, caged in etc.)
*Combat Prayer (provides spell protection and gives 8% damage boost, damage dealers love this!)
*Ward Ally/ Healing Ward (either morph is good, and it is a good way of protecting low health allies since you don't have a burst heal.)
*Siphon Spirit (if the dps does not give elemental damage, but only magicka damage then this skill is a better way of managing resources than elemental drain is. )

Destruction Staff:
*Crushing Shock (you need to dps a little in dungeons, and you can weave easily with this spell. It also disrupts casting targets, so if you see an enemy healer healing around you can stop that with this skill ^^)
*Elemental Drain (for yourself and the dps if they use elemental damage, it gives a nice amount of magicka in return.)

Undaunted:
Mystic Orb (good for providing magicka.. cast these at group members to provide them with magicka.)

Allience War Support:
Barrier (this ultimate is not needed anywhere, but if you enjoy pvp then try to lvl up to get this skill, it is veeery handy in certain situations like the Lich Boss in veteran Wayrest Sewers.)

Alliance War Assoult:
Aggressive Horn (this ultimate is not needed anywhere, but if you enjoy pvp then try to lvl up to get this skill. Damage Dealers love the boost they get from this skill.)

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You can not provide stamina to your team members in any way, unless you farm and get lucky in Dragonstar Arena or pvp, and get a Master Restoration Staff.

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You can read about the skills and how they function on this website:
elderscrollsonline.wiki.fextralife.com/Restoration+Staff+Skills