Spells like Bless, Prayer, Blessing of Fervor are good for the whole group.
Protections, such as resist energy are often better than healing since you can often protect from more damage than you can cure.
You might want to look at cleric guides for support cleric since they mostly share a spell list with you.
As far as mysteries and revelations, I don't have any at the top of my head. In general though a proactive support caster rather than a reactive healer is often going to have turns where they aren't casting, you cast a spell or two in the first rounds of battle, and then contribute in other ways, usually either melee or ranged attacks, so you might consider revelations that add to you combat capability and trust your 9-level spell casting to be good enough to buff the party (which it is).
The main thing is remembering that unless a party member is down and needs to be stabilized, their is almost always something you can do that is better than just spending your turn healing someone. You can fix them when the fighting is done. Unless you have another party member who can do it you are probably also responsible for condition removal though and you need to be prepared for that (a lot of that can be done with scrolls rather than using up spells known for situational fixes).
I'd like to make an Oracle that focuses on buffing the party, but all the information I can find is "Get the Life Mystery, take Life Link, and be Dual-Cursed for the Misfortune debuff".
What are the best options purely for party buffing, without the healing or debuffs?
Dual cursed oracle is always good for misfortune. That aside, the only mystery I found on a quick glance that buffs is the battle oracle, who has a fairly long lasting (but IMO weak) party buff once or twice per day.
That is for pure oracle, though.
You can still make an oracle who buffs fairly well by doing some lateral thinking like going into the dawnflower anchorite prestige class. Sunlight invocation, their prestige path's main feature, acts like a bard's inspire courage (max +3, but with improving action economy to swift to acctivate eventually) while also increasing the spell save DC's of allies in the aura, so it simultaneously works for martial allies as well as for caster allies/yourself. With a selectable upgrade it also increases their AC and reflex defense.
Dawnflower anchorite has two or three weaknesses, though. First, their buff only works against evil creatures. Secondly, credence, their feature which allows main class features to count downflower anchorite levels as their own class, for whatever reason does not include the oracle's. This might be an oversight of the developer and you can probably get a GM to houserule this for you. Lastly, Dawnflower anchorite grants 9 caster levels in your primary class instead of 10. So you'll need to spend a feat on prestigeous spellcaster to prevent losing spell progression.
Aside from dawnflower anchorite, if you are allowed to play samsaran as a race they have a feat which allows them to add druid, inquisitor or cleric spells (if oracle misses any) to their spelllist. Barkskin is always a good pick as are the stat buff spells at low levels. You can also get heroism from the inquisitor I.E.
I would also get a page or ring of spell knowledge at some point to get good hope, the bard level 3 spell which is basically the overall best buff in the game until very high levels. Then pick encouraging spell as a feat so you can improve this +2 to everything for everyone spell to a +3 to everything for everyone. Combine that with dawnflower anchorite, prayer and blessing of fervor and you are a solid buffer. You can do all this and pick whatever mystery you want on the side.