I will suggest Diwali. Diwali symbolises the spiritual victory of light over darkness. It is a mixture of values like togetherness, goodness, kindness and divinity and it is 💯 worth to participate in.
For the month of March Kerala celebrates Arattu festival a 5 day celebration with processions, and Kathakali dances at Varkala. Hoysala mahotsava in Belur halebid Karnataka a one day celebration filled with music and folk dances. For April
Ugadi is popularly celebrated in Andhrapradesh
Tamil new year day in Tamilnadu clubbed along with Tourism festival. Tulip festival at Kashmir which overlooks dal lake
Baisakhi in Punjab
Mopin festival at Arunachal Pradesh where local made rice wine is popular
Chithirai thiruvizha in Madurai a 15day celebration Urs festival in Ajmer
India is a land of festivals and vivid culture I will mark some famous out of them
Durga Pujo in Kolkata in the month of October (Got into Unesco intagible heritage List )
Puskar Camel fair in Rajasthan
Onam in Kerala
Rann(A white sand desert) Utsav in Gujrat from November to March
Vallam Kali(Boat race festival) in Alapuzzha,Kerala during Onam
I have explored them till date and all are completely different and vibrant on it's own✌️✌️