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.

I read that a Uttama Guru gets all the sins from His devotees the moment He blesses them. Is there anything that a devotee can do on his behalf to reduce Guru’s sufferings?

The only act a true devotee can do is to chant Nama to express the gratitude to the Guru for the grace showered on the devotee.

Which among the following is the easiest way for liberation? Guru Bhakti, Bhagavat Bhakti or building and renovating temples?

If you get a proper Guru (‘Uttama Guru’), then Guru Bhakti is the easiest way
Here are a few of numerous reasons why such a Guru Bhakti is supreme:
You can see your Guru as you see anyone else.
You can talk to your Guru as you talk to anyone else
The Guru is easily approachable
The Guru can get his ideas clearly across to you
The Guru will battle with you to make you good
God Himself says that its verily God who comes in the form of the Guru to liberate masses.
The Guru never expects anything else from you but for your love
You can visit his place and enjoy bliss and peace
The Guru can visit your place too.
The Guru will never destroy or curse anybody (even God could kill a Kamsa or a Ravana, but the Guru’s compassion is boundless)
Instead of cursing bad people, the Guru will transform them to godliness
The Guru will remove your obstacles in the divine path — both internal and external.
The Guru is the only person in the world who can do something good to you without any reason
The very sight of your Guru will help you develop your faith in God.
Scriptures say that your Soul, God and the Guru are one and the same.