Title: 6 guys, 23M, 10 days in Thailand - looking for itinerary advice

Hey everyone!
We’re a group of 6 guys, all 23 years old, travelling to Thailand for the first time.
Our flights are already booked:
14 October Arriving at Bangkok (BKK) at around 7 AM
24 October Flying back from Phuket (HKT) at 12:45 PM
So we have roughly 10 days / 10 nights to work with.

Our main priorities are:
Nightlife & partying
Best/most beautiful beaches
Beach clubs
Rooftop bars & clubs
Good party atmosphere / young crowd
Island hopping & beautiful scenery
Snorkelling / water activities
Good food and overall fun experiences
We don't really want a slow/relaxing holiday. We want to make the most of these 10 days and have the best possible first Thailand experience.
Places we're considering

Currently we're thinking something along the lines of:
Bangkok → Krabi → Koh Phangan → Phi Phi → Phuket
We were also considering Koh Samui and Pattaya, but we're not sure whether they're actually worth adding or whether we'd just be wasting time travelling between places.
We're especially interested in Koh Phangan because of the beaches, island atmosphere and nightlife, although we're not going specifically for the Full Moon Party.
What would you recommend?
If you had 10 days with flights fixed as Bangkok arrival + Phuket departure, how would you plan it?
Which places would you definitely visit?

Which places would you skip?
How many nights would you spend in each?
Is Koh Phangan worth adding in October?
Is Koh Samui worth adding, or can we skip it?
Is Pattaya worth it for a group of 23-year-old guys, or is Bangkok/Phuket enough for nightlife?
Which are the best beaches we absolutely shouldn't miss?
Which rooftop bars/clubs and beach clubs would you recommend?

We're completely open to changing the itinerary if there's a much better route.
Thanks!