It's not really all that bad as search engines go, but it doesn't do much more than searching for a specific string of text, so you're usually going to be stuck if you don't know exactly what you are looking for. If you want to use something which is a bit more versatile, I'd suggest doing a Google search with the string "site:discoverygc/wiki/" (example) included in your search query.
Alternatively, you could try using this, which is a small Google custom search engine project I started on last year which does essentially the same thing, but with a few extra features on the side. It's what I tend to use when the forum or wiki's built in search engines don't find what I'm looking for, anyhow.
Tagged words? I'm not sure what you mean here. MediaWiki doesn't have anything like that (a tagging system) by default. You would indeed be able to find the page for Livadia Shipyard if you searched for "Zoner" and looked under the "Page text matches" header, if that's what you meant, but that is a rather inefficient method for finding it.
Yeah I prefer to just use google unless im searching for something specific. Usually searching for the word I am looking for and then discoverygc seems to work
If you're typing one letter off you really can't blame it. The original Wikipedia still messes up if you get one letter off, granted theirs IS a bit more sophisticated with the predictive search bar. But yeah, unless you're looking up something like "Kusari Planets" (Hell that might even work) and you stick with using a single keyword it ought to be fine.