Castesequence and GCD

Imnew to gse and I am trying to skip my trinket which is number 13 on this sequence but i am not understanding the system I would use to skip it, can someone help please?

/castsequence reset=30 Arcane Blast, Arcane Orb, Radiant Spark, Nether Tempest, Arcane Surge, Mana Gem, 13, Arcane Barrage, Touch of the Magi, Arcane Blast, Arcane Blast, Arcane Blast, Arcane Missiles

You can’t. Castsequences only progress when a spell or item succeeds. There is no skipping. It’s how Blizzard made the ability. Your only option is to remove the trinket from the castsequence or wait till it becomes available.