If you chant it everyday, you need not chant any other Mantra. It protects you from calamities and confers upon you intelligence, learning and success.
Gayathri is Sarvadevata Swaroopini and Sarvamantra Swaroopini (Embodiment of all Gods and all Mantras) It is said, Gayathri Chhandasam Matha, meaning Gayathri is the mother of vedas. There is no need to chant any other mantra if you chant the Gayathri Mantra. Gayathri has three names: Gayathri, Savithri and Saraswathi. Gayantham Trayate ithi Gayathri (Gayathri protects the one who recites it). Gayathri is the master of the senses. Savithri is the presiding deity of the life principle. When Gayathri acts as the protector of life force, she is known as Savitri. You might have heard the story of Savithri, a woman of chastity, who brought her dead husband, Satyavaan, back to life with the power of her prayer. Savithri protects those who lead a life of Sathya (truth). This is the inner meaning. Saraswathi is the presiding deity of speech. Man has to earn the grace of Gayathri, Savithri and Saraswathi to sanctify his life.
First and foremost, man has to purify his speech. Only then will his life be safe and secure. If you slip and fall, the injury can be cured, but the injury caused by the slip of the tongue is incurable. It will make your life miserable. So, you should have control over your speech. Excessive talk will lead to untruth and unpleasantness. That is why the ancient saints and seers used to observe silence. You can uphold truth and attain fame only by talking less. Limited talk will confer happiness. Excessive talk will put you to grave dangers.
Gayathri, Savithri and Saraswathi are latent in everybody. Bhur. Bhuvah and Suvah in the Gayathri, Mantra refer to body (materialisation), life-force (vibration) and soul (radiation). Bhur means Bhuloka (the earth), which is nothing but the combination of materials. This denotes the human body, which is also a combination of materials. Bhuvah refers to the life-force which makes the body vibrate. Suvah refer to Pragnyana Shakti, which sustains the life force. This Pragnyana Shakti is known as Constant Integrated Awareness. This is also termed as radiation. All the three, viz. Materialisation, vibration and radiation are present in man. I tell you often, you are not one, but three - the one you think you are (physical body), the one others think you are (mental body) and the one you really are (Atma).
Sathya Sai Baba