You still own your own posts
First off, you own everything that you originally created. Posting it on Stack Exchange doesn't affect your rights to your own content.
If you copy any of the text from posts that were created by others, you must comply with the CC BY-SA license. The exact version will depend on when the content was posted, and can be viewed by clicking the "Share" link or viewing the post's timeline via the clock icon on the left. Currently, new posts are licensed under CC BY-SA 4.0, which requires you to (basically) provide attribution with the creator's name, a link back to the content, and an indication of whether changes were made. A more detailed description of the exact requirements is here. You would also be required to license the work that you incorporated it into under the same license.
However, game mechanics aren't copyrightable. If you merely used mechanics suggested in the posts without actually using the actual creative expression (for instance, names or description text) from the posts, you would not be required to provide any attribution or use any particular license, because you didn't use any copyrightable material from the post.
A thank-you would still be nice
All that said, it's still a nice thing to do to provide some sort of informal thanks to those who provided valuable assistance, even when you're not legally required to do so.