If you are going to spend some times in Himalayas this is the set we are usually using and its do the job very well:
1. Backpack - 20L capacity good fit for all your stuff.
2. 1 headtorch w spare batteries.
3. Running shorts, T-shirt.
4. Long sleeves shirt (merino), leggings.
5. 2 pairs of socks.
6. 2 pairs of underwear.
7. Trail running shoes.
8. Warm hat, gloves.
9. Cap, buff.
10. Down jacket.
11. Waterproof jacket, pants.
13. Hand sanitizer.
14. Water purification tablets.
15. Bladder or bottles.
16. First aid kit (elastic bandage, painkillers, plasters..)
17. Survivor blanket.
18. Mobile phone.
19. Power bank for phone (if needed)
20. Camera/gopro, spare batteries.
21. Trail emergency snacks (gels, bars)
22. Money - 20-30$ a day.
23. Your documents, Park permits (if needed, check info beforehand)
24. Trekking poles.
... Sleeping bag? - No! You'll be fine if you are using guest houses or huts to stay overnight. There is always extra-blanket options available. If not - go to another hut, you'll find one!
Some of the passes in certain time of the year requires micro-spikes and ice-ax for self arrest. You will get informed by the email if need some of those!
Thamel quarter in Kathmandu has a large choice of textile, down products and equipment to buy for a reasonable (read: cheap) prices. So don't worry if you are short of something - you will get it there!