Sir, according to me, first priority must be given to Nadikudi - Sri Kalahasti line, as it will be the shortest distance between Secunderabad and Tirupati, and also connects inner regions of Guntur and Prakasam districts which are highly underconnected.
Then after that, Kothagudem - Rajahmundry line, so that Manuguru is easily connected to North Coastal Andhra.