Hii friends im gonna tell some important points which is very helpful for buying a android devices
1) no matter how much is you budget always try to buy a snapdragon proccessor based devices because this is the best in proccessor manufacture.
2) always try to get a better battery capacity phone which gives you best possible backup.
3) and last one is camera module if you are camera lovers then you have to know the camera module that which brand of sensor is used in camera. I will recommend you like sony exmor, samsung, carlzeiz these are the best in sensor department