I use Google Drive to share video clips because they're too large for an attachment. However, there's now a way to "attach" a file using Drive when you're composing a message:

Hover over the plus icon at the bottom of the compose window, which will open the insert menu. (Remember, you need to be using Gmail's new compose and reply experience to insert files using Google Drive --- click the Compose button, click the "new compose experience" link right next to the Labels button at the top of the message.).

Click the Google Drive icon . In the window that appears, you can upload a file to Google Drive, as well as navigate to or search for files you've stored in Drive. For files stored in Drive, select the checkboxes next to the files you want to insert. Click the Insert button.
Gmail then adds a link to your message so recipients can click the link to view your file.

When you send the message, Gmail checks to see if your recipients have access to the file and will prompt you to adjust the sharing settings on the file(s) you've inserted, if needed.