Can you kindly tell me what characteristics should a Sadguru’s sincere disciple possess?

A sincere disciple will have an unshakable love for his Master. Apart from this unique quality, he should possess all the other virtues of any disciple.

What is the best offering that I can give to my Guru Maharaj?

The best offering that a child can give to his/her parents is being obedient and loving.
The best offering that a student can give to a teacher is being a performer with character.
The best offering that a citizen can give to his country, is being useful to the country in all ways and means.
The best offering that a doctor can give to his patient is providing the right medicine at the right time
The best offering that a friend can give to his friend is helping him in times of need
The best offering that a couple can give each other is perfect mutual understanding
The best offering that an artist can be given is the recognition of his merit and skill
The best offering that a devotee can give to God is unbounded love for Him
The best offering that a disciple can give to the Guru is realizing that nothing else can equal his grace.

What is expected of a sishya after he is given Diksha?

The disciple should practice sincerely what the Guru instructs. That is what is expected of the disciple.

I want to know how many Satgurus can one have in his life?

There can be only one Guru for a person.

For over a long period of time many Gurus and Sages have come and gone. There have been innumerable disciples for these Gurus. These disciples were, no doubt, devoted their Gurus, but when they move into the world, become hard-hearted, corrupt and materialistic. Why can the Gurus not change at least 10% of their disciples?

The ‘Uttama’ Guru will never try to perform any gimmicks or mesmerism to try to bring about a change in the disciple. That is the work of a magician and not of a Uttama Guru! The Adi Guru, Lord Dakshinamurthi Himself had only four disciples worth mentioning.
Goodness in any person is an attribute and is oriented towards action. This itself will not result in ‘Mukti’ (Liberation). In his great work “Viveka Chudamani”, Adisankara Bhagavatpada has said that Mukti does not result from Dhaana (charity), Sankhya Yoga or through millions of Pranayama. It results solely from Jnana and this is possible only through the grace of the Guru.
Guru’s grace is not an act in isolation but a natural result when he is extremely pleased and happy with the disciple. If that happens, the disciple is transformed spontaneously. For the disciple of a Uttama Guru to be good, all his vasanas should be destroyed. This is a silent internal transformation and is done gradually within and not through force. This may not even be noticed by the disciple himself. If the disciple is truly attached to the Uttama Guru, this internal transformation will happen slowly but surely.

When can I see my Guru, who can bless and show me a way to live? How to come over my sorrows and be blessed?

You will get a Uttama Guru some day. Until you find a Guru to your satisfaction, take Bhagavan Sri Krishna as your Guru. He is verily the Jagadguru (the Universal Master). With Sri Krishna as your Guru, continue to chant the Maha Mantra regularly. If you continue on this path, you will have a new life ahead of you.

Is it true that not a disciple but a Guru finds his true disciple?

A Guru identifies. A disciple understands.

Who is a perfect Guru?

A perfect Guru is one who has seen God and helps you reach Him.

Is it appropriate for a devotee to seek guidance from a Guru about materialistic things? Should a devotee confine my relationship with a Guru to only spiritual aspects? Sometimes I feel guilty for seeking guidance from my Guru in materialistic aspects.

Guru and God are no different. From whom else can you seek guidance if not Him? So don’t feel guilty for it. There is nothing wrong as long as your Guru doesn’t feel otherwise.

Is it possible for someone to lead a life of truthfulness without a Guru?

One has to have an enormous amount of will power to live a life of truthfulness without a Guru.