Hi Flash
I am also a new player and I had the same questions as you did. Just like Lalochezia stated, pick the crew you like and just start to learn them as you learn the game. You will get a keen understanding as to how your crew will work as well as how they will work against other crews.
I started with Raputina, mostly because of her story and the background of the Arcanists as a whole, but also because of her play style. She can sit back and pretty much wait for the enemy to get to her over a few turns while gathering up Mask Cards for my hand and her main spell. I did not know how to play the game at first nor did I know how she worked, but over time I learned to use all of her spells and select a minimal crew to support her play style. Then I figured I can use other models to gain more Melee or Ranged combat depending on the encounter and schemes. All the while asking questions. What is that, how does it work, can I do blank?
It will take time but read up on the rules and ask questions! This forum and the links Lalochezia posted (thanks Lalochezia) are great for reference.