Are you using Numbers to record anything besides how many cards you have? I saw the sample you attached. It looks like you are recording how many cards you've added per "period", and that you generally add 1-3 cards at a time. I'm not sure how the negative #s fit in - I assume you are also disposing of cards occasionally, but you aren't tracking 'when they left the collection, just that they did.
The negative numbers are the total number of cards that I am missing to complete the set. I used a COUNTIF function. If the cell is blank, it gets counted. That way I get a snapshot of how many more cards I need.
The single digit numbers are the quantity of each card that I currently have. As I open more packs, I increase these numbers accordingly.
If I dispose of a card, I will click on the individual cell, delete the current value, and type in the new quantity.
If all you want is an adding tape, then set up a long column, and in the Inspector set it so that "Return Moves to Next Cell". Put a Sum function in the bottom cell. To use it enter a '1' in the first empty cell and hit "return". The cursor will move to the next cell, and the total is incremented by one.
It's not really a "shortcut key" but there really isn't any difference hitting something like "Option+&" and "1+Return".
Start a 2nd table on that sheet near the top, with just enough cells for the title and a cell that displays that total from the Sum on the other table. That way at least you don't have to scroll to the bottom just to see your total.
I'm surprised you aren't using Numbers to actually track each card, and it's details. Once the info is added in you can do all sorts of interesting things. Sort by name, count how many names start with each letter of the alphabet, sort by acquisition date, birth date, etc etc Plus count how many players played for each team, how many were born in what month, etc etc
Sounds good, but I need to figure out this first step before adding more data! HA.
Hope this helps.