Even though it is best to learn Torah in a Litvak yeshiva where one can hear a Gemara lesson from an authentic Talmid Chacham [rosh yeshiva], if one is lacking that, I suggest getting the basic set of books that go into the depths of the Talmud. They are the Chidushei Harambam by Rav Chaim of Brisk,  the Avi Ezri of Rav Shach and the several others that are well known. [However it occurs to me that not everyone is familiar with the whole set so I might mention the others--they are the two disciples of Reb Chaim the Birchat Shmuel and the Shaarei Yosher and Even Haazel by I think the father in law of Rav Shach. ]

[However I should admit that when I was in the Mir in NY,  my main efforts were in the earlier commentaries --Pnei Yehoshua, Maharsha, Aruch Laner]-but in terms of hearing classes in Gemara I mainly heard from Reb Shmuel Berenbaum