Best ways to reduce mana cost of skills?

Given that Cast on Crit or Poet's Pen etc costs mana, what are the best ways to reduce the mana cost of the skills?

- I'm using a -9 when using Clarity Watcher's eye
- Also using Replica Conquerer's Efficiency
- Also have Deep Thoughts node on the tree plus the 10% master

Still run out of Mana. What are some other ways that I'm clearly missing.

Or is triggered spells just non-usable anymore?

If you un-hide your characters, it makes it easier to help you.

There's also using -mana on rings mods as well.

-Mana cost on all jewellery
-Replica conqueror's efficiency
-Reduced mana cost modifier on base jewellery
-Inspiration support and potentially other alternate quality gems too. For example, Anomalous Trap and Mine Damage or Divergent Efficacy
-Depending on your build, 18% reduced mana cost when hit boot enchant.
-Reduced mana cost of skills during flask effect, its a craft for flasks (search increased to find it).
-Tireless wheel, if thats in the area.

You can also get a ton of regen from rings that can help to offset high mana cost. You can look at mana cost on hit rings if your build has a high cast/attack rate and lots of projectiles, or a ring with aisling prefix life/flat mana regen (this is one mod) and high mana regen%. Example search here: https://www.pathofexile.com/trade/search/Scourge/ojj7wBkcl

This ring gave me 41 flat mana regen in 3.15

Damnation Grip
Two-Stone Ring
+18% to Fire and Cold Resistances (implicit)
+59 to maximum Life
+72 to maximum Mana
Regenerate 5.3 Mana per second
46% increased Mana Regeneration Rate
+50% to Lightning Resistance
+42% to Chaos Resistance
{crafted}Non-Channelling Skills have -7 to Total Mana Cost