Luck is one of my favourite aspects of DCC RPG and it comes from a long tradition in TTRPGs (such as from the good old Fighting Fantasy games). That said, I have one little problem with the Luck rules as stated in the DCC RPG Core Rulebook: the whiff factor. Let me try to explain this better.
I like rules that move the session forward, particularly those that make the players hold their breath before rolling the die. In certain ways, this is how I see the themes of luck, chance, fate, and doom. I remember this particularly from the classic D6 System (of Star Wars), which its Wild Dice, Force points, and Character Points. I would like that same feeling in DCC RPG when PCs spend Luck.
Actually, this topic came to my mind because what usually happened at my table is that players would roll their die and then I would ask if they were happy with the result or would like to spend Luck. And here we have two “difficult schools”. The “first school” is that of the “transparent Judge”, who lets the PCs know all the DCs and necessary stats. So, if you like to tell your players a check’s DC before they roll, then the player would just do some math after the roll and decide if spending Luck is worth it. However, if you follow the “second school” (the “secret Judge”) then that means that you do not reveal DCs (perhaps just communicating to the players that one action is difficult, easy, practically impossible, etc.), which means that PCs don’t know how much Luck they have to spend to succeed. The first school turns Luck into a matter of mathematics; the second school is a shot in the dark, which usually results in considerable frustration for players. After all, they are spending a resource for maybe no result. To make matters worse, most Judges of DCC RPG that I know (including me) use a “mixed school”: they reveal the DCs for skill checks, but not monsters' stats (such as their AC). In the end, the result is the same: either the players are doing math between rolls or spending Luck blindly.
OK, so I decided to change that. What I’ve been doing for almost two years is this: each time a PC burns Luck, they can only burn 1 point at a time. Each point of Luck is either a +1d4 or +1d6. We usually prefer 1d6s because we love to roll them, but some tables might prefer 1d4s. Why might some prefer a 1d4? Because the die explodes. That means that if roll the maximum number, you get to roll a new die and add the result (and if the second die explodes too you keep rolling).
My players so far are loving this house rule. Why?
1) It speeds up our table dynamics. I usually like to tell the skills checks DCs but not monster stats. So most of the time (with skills checks) they know right away if they want to risk burning Luck. And if they do, they don’t have to think about how much they spend: they just burn 1 Luck and roll +1d6.
2) It is clearly a risk mechanic. The idea that you know that you die might not explode works better for my players than burning blindly “X points of Luck” and feeling that it was for nothing. There is still a chance that they will burn Luck and not get enough points, but they feel the risk here is more “honest”.
3) When the dice explode, the entire table cheers! They love it! (Particularly in spellcasting checks and damage rolls).
How about Thief PCs? When they burn Luck, I let them roll +1d6 plus
the Luck Die indicated by their level. Just the 1d6 can explode. So, a 1st
level Thief burning 1 Luck gains +1d6+1d3.
Halfling PCs? They roll +2d6 and pick the best die.
This house role of course is not perfect (and it requires
adjustments when using optional Luck rules, such as Fleeting Luck, or classes
such as those from DCC RPG Dying Earth). That said, so far it has worked really
well at my tables and we are not thinking on changing it for time being.