Samsung phones under 30k

Processor-its important to look at the CPU speed and CPU type, this will determine how fast and effective your phone is.
Display- check the size of the screen, resolution, color depth, and the technology of the display such as AMOLED, etc
Camera- some of the features to check on the camera are the rear and front camera, video recording, flash, autofocusing, zooming, and more
Memory- the phone’s memory in terms of RAM and ROM and External Memory Support MicroSD
Network-2G/3G/4G
Number of SIM cards-single SIM, Dual SIM SIM
Connectivity- some of the connectivity features include USB, Location technology such as GPS, Earjacks, WIFI, Bluetooth, NFC, PC sync
Operating System-OS Android
Sensors –Accelerometer, Fingerprint Sensor, Gyro Sensor, Geomagnetic Sensor, Hall Sensor, Light Sensor, Virtual Proximity Sensing
Physical specifications such as dimensions and weight
Battery- the battery should last for hours, most batteries nowadays are not removable
Audio and Video- Stereo, Video formats such as MP4, M4V, 3GP, 3G2, WMV, ASF, AVI, FLV, MKV, WEBM, Video Playing Resolution and Audio Playing Formats such as MP3, M4A, 3GA, AAC, OGG, OGA, WAV, WMA, AMR, AWB, FLAC, MID, MIDI, XMF, MXMF, IMY, RTTTL, RTX, OTAans