Where do I go to download Instagram on a PC and how much data is it gonna take? How much does it cost?
Instagram is primarily a mobile app, and does not formally have a desktop version.
(Those who have already created an account -- normally via the mobile app -- can browse to Instagram.com on the web, even from the desktop, and access limited aspects of their account after logging in.)
However, one can run an Android emulator on the desktop, and install the actual mobile app in a virtualized environment.
One of the first solutions that enabled one to do this was the BlueStacks App Player, which can run Android apps on your desktop.
A newer and possibly better solution is Andy, which not only runs Android apps, but actually emulates a full Android environment (and can even sync with an existing Android device)!
Both emulators are available in Windows and Mac versions, and will allow you to download Instagram from the Google Play store.
If you use the Google Chrome browser there is a 3rd party browser extension that will do the trick.
It's a web-based app so the only data used is what images you browse.