With the upcoming release of the second set, Canterlot Nights, two of the greatest ways you could help to update the wiki is to start adding pages for the new cards as they start to appear, and to add rulings, errata, etc. to existing cards.
Adding a page for new cards is as simple as copying the template from an existing card page and editing the values for the template. Maybe simple isn't the right word, seeing as how each template has a lot of different variables. xD But rest assured that you can always ask me or any other member of the wikia staff on how to do this or that.
Rulings and errata are constantly changing, such that on the wiki we are constantly trying to make the rulings and errata displayed here:
easy to read and understand
have a certified source available
To that end, please don't feel offended or anything if someone changes the wording around on a particular ruling you've added; nine times out of ten it'll just be to make the ruling easier for newer players to understand or to be consistent with other rulings. If it's a ruling that currently applies to one or more card, consider making it a template and adding it to our Ruling Templates category page.
Thanks again for your edits, and please contact me if there's anything I can help you with!