Speaking very generally* and assuming whatever game it was was not extremely different from most CCG type games and that I didn't have to scan any images, then I could get a full spoiler database up and running within 3-5 days. Another 2 days for a stand alone search page.
Online Deckbuilders are a bit more work, usually it would go something like
+1 week to get something basic and workable
+1 week to specialize it to a particular game
+1 week for tweaking and closed beta test
After that point I usually make it available to everyone as a open beta for a week or two with the caveat that if any large bugs are found that I might have to reset saved decks.
More specifically about Mage Wars it does present some unique challenges. The cards have quite a bit of information on them so devising a good way to store that to make it easily searchable could be difficult. Keeping track of point costs and whether they are x1, x2 or x3 is going to take a bit of work. One nice part though is that I think quite a bit of my Netrunner code could work with Mage Wars with slight tweaks.
* all of the above time estimates are real world times and not man hours worked. As such they can vary depending on what is going on with my paid work and what is going on with the family.
