Video: 
 Om bhūr bhuvaḥ svaḥ
tat savitur vareṇyaṃ
bhargo devasya dhīmahi
dhiyo yo naḥ prachodayāt
Meaning : 
" Gayathri is Sarvadevata Swarupini and Sarvamantra Swarupini (Embodiment of all Gods and all Mantras)."
 
" Gayathri Chhandasam Matha - Gayathri is the mother of the Vedas."
 
There is no need to chant any other mantra if you chant the Gayathri mantra.
 
Gayantham Trayate Ithi Gayatri - Gayathri protects the one who recites it.