Omg noobs did I ask for rep ? Just said +REP if helped!
To me that sounds like asking for rep.
And to actually add something to this thread, I'd squeeze things into one trigger.
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Untitled Trigger 053
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Events
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Unit - A unit Gains a level
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Conditions
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(Unit-type of (Triggering unit)) Equal to Blood Mage
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Actions
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If (All Conditions are True) then do (Then Actions) else do (Else Actions)
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If - Conditions
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(Level of (Triggering unit)) Equal to 2
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Then - Actions
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Unit - Add Acid Bomb to (Triggering unit)
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Else - Actions
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If (All Conditions are True) then do (Then Actions) else do (Else Actions)
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If - Conditions
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((Level of (Triggering unit)) mod 2) Equal to 0
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(Level of Acid Bomb for (Triggering unit)) Less than 3
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Then - Actions
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Unit - Increase level of Acid Bomb for (Triggering unit)
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Else - Actions
When you level to level 2, you get Acid bomb. After that, when you level to level 4 and 6, you increase the level of the ability. This is done by utilizing modulo function.
If the (level of unit / 2) produces an integer, then the unit gains a level for that ability. For example
3/2 = 1,5 -> does not gain a level
4/2 = 2 -> gains a level
5/2 = 2,5 -> does not gain a level
6/2 = 3 -> gains a level
The same way (x mod 3) would make you gain a new level at hero level 3, 6 and 9.
So with modulo, you can easily make the unit gain a level for the ability only after x amount of level gains.
You should also make sure that you don't increase the level of the ability higher than what the max level for the ability is, since you seem to loose the mana cost from the tooltip in that case.