How can we worship Shri Krishna at home? Is it enough to install an idol, or are there other rituals that are mandatory?

the Gaudiya Vaishnavas or in general by all Vaishnavas ;

This is just my own opinion.

But if you are serious about following a spiritual path and journey ;

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begin with the simple and basic 4 Regulative Principles set out by

Pushpham samarpayami

Om Shri Krishnaya Namaha ,

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1. Offer Gandham ( sandalwood paste to the picture of statue )

2. no illicit sex (only for serious marriage, procreation and love; not for one night stands),

Naivedhyam samarpayami

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Dheepam samarpayami

But. . . to be honest with you , a lot of Vaishnavas in India and South East Asia that I know personally , at home cooks with onion, garlic, carrots . . . so yeah . . . they only avoid eggs, meat, cigarettes, alcohol and illicit sex..

Dhoopam samarpayami

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Gandham samarpayami

3. no intoxication (no tea, no coffee, no chocolates, no alcohol , no narcotics and no cigarettes),

In my opinion , anyone can worship Shri Maha Vishnu ( Naaraayana ) and Shri Lakshmi Devi. To gatekeep and to prevent others from worship and bhakthi is nonsensical. Shri Maha Vishnu Naaraayana and Shri Lakshmi Devi are not so uptight as us humans. If you look carefully at the images and artwork of Shri Maha Vishnu , he embodies all opulences , beauty, grace and powers. He is also a flamboyant archtype . . not as rigid as what others made him out to be.

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4. and no gambling (pretty obvious as this is additive forming)

Meditate and do japa and feel the immense blessings Shri Shri Maha Vishnu Naaraayana and Shri Lakshmi Devi brings forth. May Lord Shri Krishna and Shri Radhe blesses you.

3. Offer Sugandham Dhoopam ( incense cone known as dhupa or incense stick known as agarbatti )

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2. Offer Pushpham ( fresh fragrant flowers such as jasmine and red roses )

So worship away in happiness and gladness, learn how to do the simple panchoupachara puja.

Jai Hind, Jai Shri Raam , Jai Shri Krishna.

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4. Offer Dheepam ( one edible desi ghee oil lamp and one pure edible sesame oil lamp )

1. no meat-eating (including onion, garlic, eggs, mushrooms, carrots?),

5. Offer Naivedhyam ( food and drink offerings )

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The most important thing here is faith , love and devotional service. Shri Krishna is not someone whose hell bent on my way or the highway or an extremely strict disciplinary master or a psychopath. In whatever mood and approach one does, he or she or they will come to me thus Shri Krishna does not care about our measly offerings and stinking bodies even if we shower a billion times in the Ganges River. What wins him over is your faith, love and devotional service. And also with how you treat others.. if you see that Shri Krishna is in all beings , then love flows naturally and you will feel naturally blessed.