I've created a
terramancer for the Sydney campaign who mainly relies on electromagnetic effects for his magic. Channeling (Terramancy) [-2] should take care of this, together with an aspect to highlight the magnetic (and maybe gravity) part over other terramancy effects (like actually moving earth). I was looking forward to use the gravitational lense thing, too. Coupled with a photomancer you should be able to create some awesome effects.
Channeling is fast and dirty magic, if you want more substance, you'll need ritual (terramancy) [-2] as well.
There is the wizards triad when it comes to skills for a caster: discipline, conviction and lore.
Discipline is what you roll to target your spells and determine if you can gather enough energy to pull it of. I'd say it is THE most important skill for a caster.
Conviction determines how many shifts of power you can safely gather up at a moments notice. It is important mainly to be able to throw around nuke level magic as well as speed up rituals.
Lore is basically what you know of the supernatural world. It limits the power of rituals you can do without preparation as well as the strength of your enchanted and focus items.
So if you want to be good at your magic, you should put these skills on top, lore over conviction, if you want to go for the slow, heavy magic, conviction over lore if you want your magic to be fast and dirty. Discipline should be above or at least equal to both of them, whichever route you go, otherwise you are going to have to deal with a lot of backlash or fallout (either damage to you or uncontrolled side effects).
A rail gun might not be the best way to go, because you are not limited by technical issues. A staff with a detachable iron ball on top would probably be enough for a terramancer to work with. It would work more like a Gauß canon, which is not really effective in a technical application, but using magic would make it work. The staff could hold a spell as an enchanted item like Harry's rings, but instead of movement, it charges itself on the magnetic field of the earth.
The starting level confuses me a bit, which is one reason, I have not put a lot of numbers down. If you still have questions, I will be glad to help.
