New Spell Testing - Example

I've been trying to work on a spell system for my game as the people I've tested it with have not liked the current spell system.
I wanted to find/make something easy enough for them to understand, while at the same time making it at least partially versatile or modifiable for the casters.

Below is what I have so far if anyone is interested in giving an opinion as I don't know when I'll be able to get an opinion from actual game play at the moment. I've got the basics written up, and two example spells so far.

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Spell casting is a mental and physical challenge. Mana is determined by combining your Constitution score with your Intelligence score then multiplying that by 6 (i.e. 2CON + 3INT = 5D6 = 30 Mana).

All spells have a base mana cost, duration, target, casting time, and an effect; along with the ability to modify the spells attributes with an increase to mana cost.

Just as INT contributes to how much mana you have, it also affects how much mana you can manipulate while casting a spell. When you cast a spell normally or with manipulations the amount of mana you can put into a spell is equal to your INT times 2 (i.e. if you have 2INT then you can only put a total of 6 mana in one spell casting attempt at a time (2*3=6)).

Casting time is split between short spells and long spells.

Short spells are capable of being cast quickly, meaning you can cast them on your normal initiative roll without any penalties. This means you can move up to your normal speed and still cast the spell easily enough.

Long spells however require more concentration; when you cast a longer spell you have to focus on the spell, meaning you can’t move from your current position without interrupting the spell. Moving while casting a long spell incurs a penalty of 5 black dice for every 5 feet. Also when casting a long spell you take a small penalty to your Initiative roll which is dependent upon the spell being cast (on your initiative turn you state what you are attempting to cast, and then apply the penalty to determine when the spell takes affect).

 

Spells

Elemental Weapon

Cost: 3
Duration: 1rd per INT
Target: 1 weapon touched, or 1 clip of ammunition
Casting Time: Short
Effect:
You form an energy field around the end of the weapon that radiates some form of elemental energy. When cast you choose: Acid, Cold, Fire, Force, or Shock. When someone strikes something with the weapon or ammo you touched it deals an additional 3d of damage of the element you chose when the spell was cast.
Modifications:
Double duration: 2rd per INT. +1 cost.
Double Target: 2 weapons touched. +1 cost.
Increase damage: +1d. +1 cost.

Skill Boost

Cost: 5
Duration: 1minute per INT
Target: 1 person touched
Casting Time: Long -5
Effect:
You touch a creature and give them a +5 boost to one skill that they currently have 4 or more ranks in. When you touch a creature or person you temporarily unlock their future potential with a  skill granting a bonus for a short time.
Modifications:
Increase Duration: 1hour per INT
Increase Bonus: +1rank. +2 cost