User blog comment:Shirubakun/Deck Ratios/@comment-4292163-20140331214137

There isn't one auto-build ratio that works best, but there are overarching patterns to take advantage of.

For monsters, assuming your goal is to form a full field consistently, I recommend 22-28 monsters, which should realistically provide a 70-80% chance of getting a full field. Run as many size 3s as your strategy allows (usually just 3-4 due to gauge issues) and use 2-4 more size 1s than size 2s.

For spells, most if not all worlds have 3-4 "staple" spells that you need, plus a few spells your deck specifically needs. All together, most decks run 18-24 spells.

Impacts, similar to size 3s, are usually run at 3-4 of due to gauge issues. Their "I win button" nature means that people rarely cuts them except for gauge reasons.

Items... items are all over the map. I'm not even going to try to predict them.

I'm sure most decks don't follow all of these rules, but you'll be hard-pressed to find a deck that doesn't follow most of them.