I may not be the GM, BUT allow me to assist you with my own thoughts and answers:

[quote=@Valor]
1: The Fairy Tale wiki barely mentions anything about mage ranks or what kind of power they would have aside from "A lot." Could someone please clarify what exactly the standards are for this thread?
[/quote]

Ok.

1). It's Fairy TAIL not Tale (Sorry I had to do that)

2). There's a ranking system among mages that coincides with what powers they possess. Depending on the power and at the skill they use them, they can be placed in the following ranks below, starting with the highest:

[b][s]S-Rank:[/s][/b] A true professional. Beyond simply being competent, they bring something to table that the rest of the group don't have. Something that makes them a cut above the rest. That is the minimum requirement in order to merely survive against the threats they are expected to face. 

(Note this magic amongst anything over it is forbidden from this RP currently)

[b]A-Rank:[/b] Mages who have proved their talent against the norm. Struggles in combat against higher ranks, but can pull out victorious. Examples include: Lucy Heartphilia (Celestial Spirit Magic), Freed Justine (Letter Magic & Eye Magic), Juvia Lockser (Water Make), Elfman Strauss (Take Over: Beast Form), Natsu Dragneel (Fire Dragon Slayer), Gray Fullbuster ("Expert" Ice Make currently in the manga), Erza Scarlet (Spatial Magic (Requip: The Knight), Sword Magic, Telekinesis),  Mirajane Strauss (Take Over: Satan Soul & its respective forms), Wendy Marvell (Sky Dragon Slayer Magic), Gajeel Redfox (Iron Dragon Slayer), etc. etc.

[b]B-Rank:[/b] Mages of Slightly Above Average talent who can put up a fight against A-Classes while going all out. Examples include: Evergreen (Fairy Magic), Cana Alberona (Card Magic), etc.

[b]C-Rank:[/b] Mages who can't compete with A-Class and have trouble against B-Classes. Considered weak in physical power by the higher-ups of the Wizardry world. Examples include: Jet (High Speed), Happy (Flight, "Fire Magic"), Lisanna Strauss (Take Over (Animal Soul - "Note that these transformations are weaker than Elfman's Beast Soul), etc.

You can find a full list of ranks and which characters fit in which here to judge upon what you want to do [url=http://fairytail.wikia.com/wiki/User_blog:MarineroLelouch/Power_Ranking_and_Classes.]here[/url].

[quote=@Valor]
2: Would this work?

The character I'm planning would be a "leader" type character. If you've played Dungeons and Dragons, think of the Warlord. [url=https://i.pinimg.com/originals/02/1f/aa/021faa230e4508c89a7aaa1c63f300dd.jpg]Here's her image.[/url]

The main thing I'd be thinking would be something along the lines of "shouts of power" or something akin to that. Like in the original Dawn of War where, if you upgrade a squad with a sergeant and use his "Rally Squad" ability, he can shout several things like "You will stand your ground!" and "Rally Squad!" among other things. [url=https://youtu.be/hqFcGhQ1V4A]See here.[/url] and [url=https://youtu.be/nb6cSEI1FLk]here[/url] for examples.

I was going to have the "shouts of power" be caster magic, though disguised as holder magic, specifically the gemstone in the pommel of her sword. The other thing would be a sort of "Repair" magic, which would keep her equipment in good shape and allow her to heal faster. 

Would that work? 
[/quote]

Now I haven't played Warhammer admittedly, but considering how familiar I am with said genre, that sounds more like giving orders than well just magic stuff. You could maybe have the character manipulate some army of (lets say Skeletal) soldiers of some kind and your commands may give them buffs regarding the situation. Idk about being solo regarding other characters though... although you may want to look at [url=http://fairytail.wikia.com/wiki/Orient_Solid_Script]oriental solid script [/url] and [url=http://fairytail.wikia.com/wiki/Sound_Magic]sound magic[/url] for other ideas. These all come across words and letters being put into a magic of sort. 

"Repair" Magic can be a thing, according to this one little fanon article [url=http://fairytailfanon.wikia.com/wiki/Repair_Magic]here[/url], although you should talk to the GM about this first.

[quote=@Valor]
The Wiki and watching a few episodes doesn't really bring a lot of clarity to what you can and cannot do.
[/quote]

You're going to need to watch waaaaay more episodes to get the grasp of what magic abilities can be used - or just use both the canon and fanon wikis for reference (but be aware of spoilers if you're that interested in the story).

Either way, I hope I happened to be of useful help to you :)