"Tovim" is the plural form of "tov," one of the most familiar words in Hebrew. Tov means "good." And, like the word good in English, tov brings a multiple of inferences.
When we describe someone as a "good person," we generally mean that he or she is moral, upstanding, or well-behaved by some standard. The exact nature of this meaning depends on context, obviously. There is a subtle difference between the describing the local hero as a "good man" and the well-behaved child as a "good girl."
When we suggest that an object is "good," we generally mean of high quality, pleasing taste or desirable function. "That's a good strawberry" means "that strawberry tastes delicious." By slight contrast, "that's a good car" means "that car is dependable, economical and/or safe."
And when say that something is "good for you" we mean to say that it brings a benefit of some kind that improves your situation.
While I think I could make a case for either of the first two meanings in the phrase "gomeil chassadim tovim," I think that mostly you will find that the third meaning – beneficial, enhancing – iwhat "tov" means in most of its usage in the text of our prayers.
Think of it in terms of other colloquial uses: boker tov, laila tov, mazal tov. When we wish someone a "good morning" we are not wishing the morning will behave like morning should; when we say "laila tov," we are not expressing the hope that the quality of darkness will have that je ne sais quoi. Instead, just as the phrase "mazal tov," literally "a good constellation," we hope that the circumstances in which you find yourself will be to your benefit.
Next we will try to put together the entire phrase "gomeil chassadim tovim" and see how the three concepts fit together in describing God.