Hi, concerning mage class:

Am I able to use whatever magicks I choose to or am I limited to the spells in the shop? And where do I start roleplaying, exactly?

A tough one, you are able to substitute a spell that is not in the shop but you have to get a spell that would seem to be the closest to it. Ex. If you want something like Acid Breath then Frost Breath would be alright for it.

Also, you can start by posting on the IC forums anytime you'd like. The Tavern Hall is a great place to find someone to post with and for new people, I'd recommend going here, The Greenhouse Guild is nice since you can also make some extra silver here. 

Like Xunatar said, we're fairly lenient on spells depending on if you can make a logical case that a spell is similar to one in the shop. We do have some global reservations (like you can't use blood magic unless you have a custom or event item that has been approved to allow it), but we're pretty open on what you can cast.

Some examples:
Conjure Earth Elemental subbed for Conjure Slime
Ice Breath or Fire Breath subbed for Acid Breath

etc.

If you are ever unsure about a substitution, you can just ask in this Help Forum and other members can help you figure out a sub.