Gaining adverbs are provided in this article. The words listed here are commonly found along with the verb gaining in sentences. This reference page helps answer the question what are some adverbs that describe or modify the verb GAINING.
actually, apparently, clearly, constantly
continually, currently, daily, eventually
evidently, finally, gradually, increasingly
merely, quickly, rapidly, really
simply, slowly, steadily, surely
ultimately
Hope this word list had the gaining adverb you were looking for. In addition to adverbs used with gaining, other example verb adverb pairings can be found on this site.
You can help by adding more adverbs in the comments. Thanks.