This is a Survivability-based build for Seris.
Increase the range of Restore Soul by 300% and the Duration by 1s.
Reduce the Cooldown of Restore Soul by 2.5s.
While channeling Restore Soul you heal yourself for 70 Health per second.
Fade to Black
Activating Restore Soul reduces the Cooldown of Shadow Travel by 2.4000000000000004s.
Reduce the cast time of Shadow Travel by 45%
Increase your movement speed in Shadow Travel by 60%
Gain 30% Movement Speed.
Increase your Mount Speed by 45%.
Reduce the Damage you take from Direct attacks by 21%.
Reduce the Damage you take from Area of Effect attacks by 21%.
Reduce the duration and effectiveness of Crowd Control and Slows by 90%.
Your weapon attacks deal 225% increased Damage to Shields.
Your weapon shots reduce the effect of healing on your target by 90% for 1.5s.
Soul Forge 5
This is a MUST HAVE card for Seris, she is completely useless in a Support role without it.
Blood Pact 1
I used to run this at a higher level, but overtime I kept dropping the Blood Pact level from 3 to 1. I could see lower elo players finding this useful if you can't properly keep safe.
Fade to Black 3
This is what the Blood pact levels got replaced by. This allows you to get Shadow Travel off cool-down in two full Restore Soul channels.
This is what I'm used to, you can get away with more or less Veil. I'm just too used to running Veil at 3 to change it at this point. Put leftover points into your preference.
Dark Whisper 3
This is something I see many lower elo players not run at all or not run at a high enough level. Without Dark Whisper you can't go anywhere in Shadow Travel and you will just die and waste time. Highly recommend to put more points into this.
Nimble is a key asset to Seris, as she doesn't require Chronos to perform her role. Nimble is one of the best options available to her as it allows you to keep distance from enemies, re-positioning to get line of sight to teammates swiftly. I practically always strive to get Nimble 2 before anything else.
Master Riding 2
This is something I didn't use to buy much before, but with random matchmaking, teammates won't always fall back if the support gets picked off. Having Master Riding will help you bail them out if they survive long enough that you have time to re-spawn. Seriously. Give it a try. It's more useful than you think. Getting more than Master Riding 2 is kind of a waste though. Opt for this if no Offensive or Defensive items are needed to have a chance of winning.
After these two main items, it's really up to the situation.
If you're being hit by Direct attacks, pick up Haven, If you get hit by Area of Effect attacks pick up Blast Shields. If Crowd Control is a problem, pick up Resilience.
As a Seris, you will be more or less constantly firing between heals. Cauterize and Wrecker are both fine options as you just kind of throw shots in the vague direction of the enemy team.
If there's no need for you to pick up Cauterize. Pick up Wrecker. It's genuinely a good item for Seris since it's the only thing blocking your Ultimate and weapon attacks since your shots are going in the general direction of the enemy team in the first place.