Welcome!
A good fit for a system depends on several factors. What are your goals? What is your tolerance for challenge and what kind of time can you commit to learning this new skill?
Many people begin with a single digit system but rapidly realize the limitations and inefficiency there. Very quickly they’ll move to a 2-digit system.
At its most basic, a 2-digit system gives you an image for every number from 00-99. This is 100 associations to learn. May seem like a lot at first, but really isn’t too bad. With consistent practice you can get serviceable with it in a couple weeks. (While you’re at it, create images for the single digit numbers 0-9 too if you skipped directly to a 2-digit system.) This way you’ll be ready for a string of digits with an even or odd amount of numbers.
You’re right, there are many styles of system and ways to encode your numbers or cards into images. I advocate for using a phonetic system, specifically the Major System. The phonetic rules are pretty straight forward and with a couple weeks of practice should stick easily. With this phonetic foundation established, you’ll be able to “read” numbers and cards as if reading words. By practicing associating your list to the numbers you’ll start to advance in fluency of your new vocabulary. Just like you see the words that are written in this post and don’t really have to actively think about reading and sounding them out, you can get that way with a phonetic number system given enough practice.
Now after a bit you soon may realize that just having a single image for each number isn’t that efficient and you may want to expand the system to fit a Person/Object or a Person/Action or a Person/Action/Object structure. Doing this will allow you to quickly see a series of digits and translate them into an active scene that is vivid and easy to recall. Then its just a matter of decoding the elements of the scene back into the numbers that they represent.
For this, I love being able to use a consistent encoding process for all of my elements. For my 1 and 2-digit system I based all of my 110 people, 110 actions, and 110 objects directly off of the major system phonetics. This way I can see a set of 6 digits like 341147 and simply read it as MaRy (34) TooTing (11) on a RoCK (47). This generates a memorable scene and boom, 6 digits memorized in a matter of a second or two. Give each scene context via the loci method and you can string together sets of digits. With about 17 scenes you can get 100 digits memorized or all the images for a full deck of cards.
You of course don’t have to go with Major or a phonetic system at all. You have probably seen lots of other options discussed here. I’m sure Fred will chime in with his vote for Dominic’s initials-based people generation or an “uncoded” system that just relies on previously learned habitual associations. Many will advocate for a traditional PAO system where just the People are built from a specific set of conversion rules and then the actions and the objects are first associated to those people which then can trigger the number or card recall. All of those systems work ok too. Any system can eventually get you to the end goal of instant association, see the number and reflexively visualize the image. I just think some structures lend themselves to a simpler learning process with less built in conversion habits that will need to be corrected later.
For me, the least different conversion techniques involved in your system the better, and the fewest conversion steps to get from element to number the better.
I personally like full Major PAO because it excels in both of those areas. The only “conversion step” you need to learn is the phonetic rules for the 10 single digits. With Major, you can use the same image list for cards AND numbers, the associations for all elements in the list can be learned directly to the numbers or cards right from the start, and it is fairly future-proof if you want to expand into advanced techniques down the road like a 3-digit number system (1000 images).
If you want to see what a full 1 and 2 digit PAO based on the major system can look like, check out this post:
For more on the idea of independent association of elements when learning a system, specifically a PAO, give this a look:
Remember, everyone’s brain makes connections in slightly different ways and different systems resonate differently for everyone. You can have success using just about any system if you practice consistently with it.
Don’t worry too much about “picking the wrong one” and just pick one and try it. Don’t worry about wasting time or setting yourself back if it doesnt fit. Remember, you’ll learn about yourself and your learning strengths as much with failure as with success.
If you approach system building as a personal challenge and an opportunity for mental exercise, much like people like to do sudoku or crossword puzzles, you can find enjoyment in the process and hopefully get over the indecision factor.
Good luck, whatever you choose!