Try to build a hardcore flex build for my GA

[Rin1604]

As the title said , im trying to make a hardcore flex build for GA ~~~ mainly boost my favourite skill SIEGE <3
Here are what im thinking about :
-10% flex dam skill stack = 50% (now i have only a 8% , but i will buy a 10% next weekend)
-10% from erada chronicle (i wish i had farmed this before the revamp =.=)
-20% from skill ring
-35% from 100 erp points
-10% from any heroic piece which has siege dam idened (too much rng =.= i wont count this)
Im also wondering about getting lowe title too (+20% active dam skill) to replace with my Shadow decent but i dun know if it is worth my time deranking from near SSS to B-A.Is there any more way to boost flex dam skill?

[AquaTail]

Skill cut ins and custom awakenings also have a 1% boost option

[Valaera]

Instead of Lowe's title you can go for Apple's Ancient History, 20% more damage on actives and +200 mag attack.

Other things that give +active damage:
+5% from wild tracker top piece
+10% from 4/5 wild tracker set
A few skill cut-ins and awakening animations as stated by AquaTail

And since you aren't listing +all skill damage:
+5% for 2/5 heroic wrath set
+10% if you wear 3 more pieces
+10% if you have a stage 15 void weapon
+5% if you have a +11 void weapon
Some IB sets, like Rosso have +7% for the 5/5 set and another +5% for 3/4