Unfortunately, there is no proper answer to this question. In reality, GATE qualifiers are preferred by JNTUH over PGECET rank holders. Even Rank 1 in PGECET can not guarantee your admission to JNTUH.
But to give you a concrete number, you must get at least rank 50, unless you want a less popular branch like Biomedical Engineering. But then again, most of the seats are filled at JNTUH by GATE qualifiers.
It will be better if you prepare for GATE instead of PGECET, to get an M.Tech seat in JNTUH or Osmania.
Telangana conducts its own state-level postgraduate entrance test called Telangana State Post Graduate Engineering Common Entrance Test (TS PGECET). However, for admission at Jawaharlal Nehru Technical University, Hyderabad, they give preference to students who have GATE scores rather than TS PGECET.
So this is very unpredictable and there is no certainty that you will even get a seat. The best thing you can do is score a rank in the top 50 in TS PGECET and hope. You may get less popular subjects such as Biomedical Engineering.