It's true that many mainstream apps (like Google Chrome, Instagram, Snapchat etc.) are not included in Windows Phone App Store. That does not mean that there are not many really good apps and a few alternatives for famous apps.
These are the apps that you absolutely should have installed on your Windows Phone:
UC Browser:
This
Browser has everything you need. It is fast, safe and reliable. It offers incognito mode, night mode, bookmarks and all the features you would ask for.
You can download it from
here.
Dropbox:
Dropbox is the best way to keep a
back-up of your files and have all your data accessible from all your devices (PC, Laptop, Tablet etc.)
You can download it from
here.
Windows Phones do not have an official
YouTube app. Although, this is a very good
alternative, which also offers some extra cool features. You can download videos or save in an MP3 format the sound of the video. You can also lock your screen and continue listening to the sound of the video!
You can download it from
here.
You can download it from here.
Viber:
The famous Viber App, is the best free way to chat, video call, or simply phone to anyone is on Viber.
Just download the app, follow the easy steps and in a few seconds you are ready to go!
You can download it from here.