It's hard to say, because Black Company's magic system is WAAAAY different than D&D's. In essence, dabbler allows you cast a few rudimentary spells, but gives you NO bonus to do so, and since it's skill based, it's a pretty slim chance of success. You have a Magic Use Skill to put points in, and you roll a magic use check to cast a spell. Basic cantrip like spells start at DC 10, and you must take feats or class abilities to get each spell. The higher the roll, the more you can add into a spell, like better range, bigger effects, more damage, greater area, etc. Other abilities (Student of Wizardry, 1st magnitude, 2nd magnitude, etc.) give you bonuses to cast.
The best way to think of it in terms of D&D is like the Magical background feat from Forgotten realms, where it gives you a few cantrips. Or more likely, think of it as giving you the ability to cast 1st level spells as a first level wizard, and no higher.