Go for a true 2-digit list if you’re even remotely interested in applying this technique in anything more than just a passing curiosity.
Staying with a 1-digit is like being interested in the piano but only barely learning how to play a single note at a time with one hand and then just stopping there, playing only Mary Had A Little Lamb for the rest of time. With just a LITTLE bit more time and effort, you can open up so much more variety, practical functionality, and enjoyment.
I only really recommend a single-digit list as an introduction to help people learn the broader technique of converting abstract numbers into solid visuals, or if using a phonetic system, to help initially learn the number sounds. Once that understanding is reached, a 2-digit system should follow shortly. Even if you aren’t interested in competition or speed challenges, you should go for the 2-digit list. The benefits are so much greater, even for beginners or casual users.
If you start with a simple Person/Object list, leaving out set actions at first, that’s only 200 associations to build and learn. That may seem like a lot, but once you start I think you’ll find it’s actually not that bad. If you learn 50 new associations per week (25 people and 25 objects), then within a month you’ll have seen them all and can start fully implementing them in practice. Don’t underestimate the power of your brain to do be able to handle this.
(Important: don’t pick the people AND objects for the sets of 00-24, 25-49, 50-74, 75-99 to learn… Pick the people from one set and the objects from another each week. This way you’ll be learning to associate those element types INDEPENEDENTLY of each other, directly to their number. So instead of 11 being ToDD with a ToaD, 11 is ToDD when it is a person and it’s a ToaD when it’s an object. A small but important distinction. More elaboration on that here.)
Yes, it will take a little longer to get familiar with the associations, but the advantage it confers is huge compared to a 1:1 encoding system. You can get twice as many digits encoded with the same number of elements. Would you rather have to keep track of 8 elements to memorize a 16 digit credit card number, or 16 elements? A 10 digit phone number only takes 5 elements instead of having to keep track of 10.
Remember, the important factors of a number system are how many digits can be encoded into a SINGLE ELEMENT and also how few mental conversions you need to go through to translate a number to its associated element and vice versa. You can cram many ELEMENTS into a single SCENE, but you’ll still need to encode/decode each element accurately and in order. It’s much more effective to encode 4 digits as a scene containing two interacting elements that each represent 2-digits than it is to encode 4 digits as a four element scene. More on ELEMENTS vs IMAGES/SCENES and SYSTEM terminology.
The trade-off is the effort spent in building the 2-digit system, but realistically speaking, wouldn’t you rather take a couple extra weeks at the beginning during the learning and building phase to ultimately save yourself TONS of effort, time, and frustration once you start using it?