It would make sense that Kaguya would be the first gates user. I didn't think about this before, but now it seems kinda obvious. You'd obviously use new found power in a way familiar to you, in Kaguya's case, it would most likely be taijutsu and kenjutsu like you said. Now, to be honest, I don't think the gates gives power similar to the fruit. I think it's just a teachnique and nothing more. That aside, it is possible Kaguya had it.
If I were to guess the abilities Kaguya would be likely to use, it would be regen, chakra enhanced fists, advanced body flicker, the samuri's technique chakra focused through blades, and the gates since they're all physical in nature. However, considering her son was beyond what normal people could achieve (rinnegan and creation of all things) it's safe to assume each of these techniques would be at a whole new level compared to what we've seen.
Edit: A lot of people are saying that taijutus has nothing to do with chakra, but here's the thing, the gates are chakra restricters, so there's definitely taijutsu influenced by chakra.(although not all taijutsu is)