should i wait for 1-2 day after sale start or order today after 12 pm ?

As I observed after few days of sale good offer/ Discount will appear.

I think it's better to order at the earliest or else the delivery time would increase if ordered a day or two later as sellers would be dealing with a lot of orders. I have heard the best deals are on the first day of the sale but never experienced it as for me it remained the same a day or two or maybe even on the last day. Products might also go out of stock pretty quickly if you wait & maybe other sellers' deal are a bit expensive than the ones you could choose at the beginning of the sale 

Purchase items as soon as the sale starts. Prices going to shoot up within 2-3 days of sale.

its depend on product and flipkart mood, once i needed a suitcase which usually goes for 1.8k, early bbd sale starts that was available for 1.6k i thought fine will order tomorrow and next day ordered at 1.7k (price increased), in the following days prices increased to 1.8k-1.9k to 2k final lol they do this type of shits with even normal products in bbd only

in 2020 tv days sale had opposite experience, samsung 32 inch was selling for around 14k in first day, next day someone came with supercoin offer or something and price dropped to 12k, next day another better offer came price falls to 11k i thought let's wait for another day and next day with more offer price falls to 10k (this is without any bank discount), many got xiaomi tvs for 8k with bank offer and what not just by waiting till last day 

As per Flipkart CS, for items that had the Price Lock option, those deals won't be available to those who didn't utilize the option

simple answer in my opinion

a) Flipkart: fake offers by stickering in limited numbers, so  if its flipkart go by first come first serve

b) Amazon: price is usually not that discounted, so if its amazon, buy at your own leisure before the end of the event

High demand products will be priced lowest during initial hours, better buy at the earliest.

its all pure luck