Help getting authentic peices

Hi, I've decided to get my first perfume. Have gone through a lot of threads here, and have finally gotten my head around Blind-buy, EDP, and fragrance related terms.

I am curious about the resellers of the community. Isn't it more feasible to get your drops directly from Myntra, Nykaa, Ajio and so on. Why are the resellers so prevalent?

And lastly, I looked at Afnan 9 PM and Rayhaan Lion. As per the reviews, I found that Lion is a little more liked in the price range. Is it a blind buy or I must get a 5-10 ML bottle initially.

Since I've not been exposed to brands/fragrances ever, I feel I may not be able to judge if this smell goes with me well or it doesn't since I've no awareness anyway. Does it make sense to get 3-4 different decants and try them on?

Thanks for all the help!