This takes too long building things one at a time. Is there a way to get another building slot? By research? By coins? Gems? I need something.
Nope. You can only ever build one building at a time.
But there are ways to increase your building speed:
• Research (Look under Economy)
• Talents (On the right side under Food Production)
• Heroes (FTP: Sage of Storms and Scarlet Bolt; P2P: The Big Guy and Witch Doll)