Deck Design

A deck has a specific overall function. It's not just a pile of the coolest cards you can think of.

Simple

Most of the cards in your deck should be very simple.

If you want to give the player more options, give them more cards, not more complex cards.

In my farming game, the gameplay really needed each player to have ten objective cards in their hand. That's a lot of cards, but it was doable because I made each card ultra-simple. Almost all are just an icon with a number in front of it.

What are the simplest possible cards that could exist in your game? They should probably exist, because their complexity is super-low, and their gameplay value might be reasonable. Many of your cards should be nothing more than an icon. Most should be one sentence, plus maybe an icon. Next, do cards that have two icons on them, or an icon and a sentence of text. Then, two sentences.

Not all of these cards will work, but you should try them.

Straightforward

As well as being simple, most of the deck should be composed of cards that do very straightforward, basic things, like give you resources, or other basic actions. They shouldn't be situational or unusual or flashy. They should be things you'd usually want, even if those things are boring on their own.

The hand as a whole is what's interesting, not the individual cards.

When players draw a hand of cards, it should be very easy to understand, useful, and maybe have one wacky or exciting card.

A properly-designed deck will be mostly boring and functional.

How many cards?

To further simplify the deck, and make it more functional, I usually skew card decks heavily towards the aforementioned simple & straightforward cards. I put three to five of those cards in the deck, and only one or two of each of the exciting and strange ones.

I try to keep decks as small as possible, if the deck isn't the core of the game. You can easily make a deck much better, by halving its size, and keeping only the best half.

Predictability

There's also another axis to consider here: predictability. I usually like players to have some idea of what cards the opponent will play.

If there are some common cards in the deck, a player can anticipate them, and strategise accordingly. If the deck is full of unique cards, players won't be able to strategise at all. The opponent's cards will just hit them out of the blue, and it will be feelbad.

My gangster game has a small deck of few cards. These cards are not supposed to be the centrepiece of the game. Players can weigh the probabilities that their opponent might have a certain card.

In my adventure game, the decks are the centre of the game. The game is about discovery, not strategy, so the decks are much more varied.

Use a deck

A general piece of advice here: Cards do a lot of good things for a game. They provide choices. They're a well of depth and replayability. They help tie turns together. If the cards are in players' hands, they're hidden information, and which pushes your game away from calculability, and towards intuition.

Most games should have a deck.

Deck construction

Avoid "deck construction" (this is where players can modify or build their own deck before the game.) Many players will not want to play a complex metagame on top of your game. Deck construction also likely requires multiple products, to enable the full spectrum of deck-construction possibilities. It probably also necessitates a community, where you can trade for cards you want for your deck. The vast majority of players don't want to interact this strongly with a game, or do non-game activities. If they do, they can just play a game like Magic, which is designed specifically around that concept. Publishers are also likely to shy away from competing with the giants that already dominate this field.

Just make a normal game.