In SR5, you have to know the ritual for summoning one, and be ready to pay a lot of karma. (8xForce + extra for extra skills, such as Counterspelling and Spellcasting). Furthermore, one must first have initiated into the school of Invocation to be able to learn the Ally Conjuration ritual, so unless your GM allows initiating in chargen, you can't get an ally spirit in chargen. On the bright side, you could use Familiar as Ordeal.