You can read the descriptions of the items and assess how useful they will be to you. For example, giving him the gloves of thievery, which gives you an advantage on stuff like lockpicking, would be a terrible idea, while giving him the ring of color spray, which offers you a level one spell that I personally never use, would be a smarter decision. And the gloves that Zakrug drops during the battle outside the grove seem almost tailored to Gale. Because you have to have the “absolute brand” on you for them to work. And probably only a tiny percentage of people will let themselves be branded… I don’t have any problem at all with giving him three items, considering the massive skills that he brings to the table as a wizard. I mean, have you ever used a chain lightning? Lol. What he can do makes it more than worth it.
I'm talking about a first run specifically. NOW I know what to give him, but that wasn't always the case. The moment you get the Gloves of Power you don't know what an "absolute brand" is, and the description of the benefits looks inviting. It even has a +1 to Sleight of Hand. Most of the early magic items are in the "maybe I will need this a bit later" or the "better than what I already have" category.
This sacrifice could have been worthwhile if Gale was more than a generic wizard. There is nothing special about him from a gameplay perspective. You are better off with the blank hireling wizard Withers provides.
He doesn't even have a proper personal quest.
