What is aim of worshipping?

The sole aim of doing worship is to attain liberation or Moksha. Liberation or Moksha means getting freedom from the cycle of birth & death. 

Whom should one Worship?

Some people worship Shri Krishan (Lord Vishnu, incarnation Ram), some worship Goddess Durga, others worship Lord Shiva, some worship deities like Ganesha, Hanuman etc. The cardinal question with the devotee soceity is "Whom to Worship?". Then there are other religions like Christianity who worship Jesus or Mother Mary. Some religions like Islam worship an invisible God whom they call "formless" and have no clue about anything. 

The crucial question is whether this worship of any use. 

The fact is that the worship of Brahma, Vishnu (Krishan, Ram etc.), Shiva, Durga, Hanuman, Ganesha and other deities is not in accordance with the Holy Scriptures i.e. Shrimad Bhagavad Gita & Vedas. Henceforth this worship is not of any use i.e is not going to grant a devotee Moksha / liberation. 

According to the Scriptures, Supreme God is Kabir. So for a worship to be successful, one needs to worship Supreme God Kabir. In fact, God Kabir is the only God worthy of worshipping. This is what Shrimad Bhagavad Gita says, Vedas dictate, Quran says, Bible says and Shri Guru Granth Sahib says. 

How should one do Worship? 

To do true worship, one should take initiation (naam) from a True Saint and then do worship as told by the True Saint. Acquiring a Guru is paramount to doing worship and attaining salvation. Find all the information about Initiation here.

Should Worship be done with the sole aim of curing deadly disease or achieving wealth / materialistic gains?

No. See above. The only aim should be achieving moksha.

Then How can one get rid of deadly diseases by worshipping?

Getting relief from deadly diseases is a by-product of true worship. These happen automatically. There are 4 sequential fundamental conditions which have to be fulfilled first to attain this benefit. These are as follows.

  1. Understand the knowledge given by Sant Rampal Ji Maharaj.
  2. Develop full faith in the fact that, Lord Kabir is Supreme God.
  3. Take initiation from Sant Rampal Ji Maharaj and do worship as ordained by Sant Rampal Ji.
  4. Follow the rules laid down by Sant Rampal Ji very strictly.

If the above mentioned four points are followed, then a devotee derives all the benefits as have been written in our holy scriptures.