I wouldn’t combine those decks.
Encode and Decode are two different functions. You use Encode to practice seeing the number and checking whether you visualized the correct element to go along with it. You use Decode to practice simulating recall where you’d have a mental image that you need to convert to it’s number.
By training both ways you’ll strengthen your recall speed.
Have you looked at the structure of how the cards are separated into decks and how they are tagged in Anki yet? You can set up a filtered custom study session to include both Encode and Decode cards if you want without changing any actual deck or tag organization.
I’d recommend starting with the Encode cards. Give the first 10 a go for a couple days, then add the next set in as I outlined previously.
Don’t overthink it.
Just start looking at the numbers and testing yourself to see if you can correctly picture the associated element. For the first 10 digits, you only have 30 elements to learn.
Regarding your question about using multiple languages in your list… Nothing wrong with that at all! As long as the images that you are associating to the numbers make sense to you, then you’ll be just fine! Remember, you’re trying to see the number and not just say or recall the WORD, you’re trying to be able to quickly visualize the IMAGE that the word conjures up.
So if your 16 word is DiSH, you don’t want to simply read and think “dish,” you want to make sure you’re actively visualizing a specific “dish” in your mind. Maybe it’s a porcelain china plate or maybe it’s a satellite dish, whatever it is, make sure you picture it as you read your number/word. Eventually the number will “become” those images and then you’re really getting somewhere!
As for your memory palace question, nothing “wrong” with that either. It can also help lock in the images. I’d recommend 10 distinct areas with 10 unique loci each. That way if you’re trying to recall 73, you move to your 70’s area, and count through loci to 73 to find your image.
The only thing I DON’T like with the memory palace approach to learning a system is that in the time you’re spending navigating to the right loci, you can weaken the direct connection from number to image. So if you see 73, you really want to try to directly make that connect to the image.
“Object: 73 = G-M = GuM. 73’s object is GuM.”
Compare that to:
“Object: 73 = 73rd loci = 70’s Palace + 73rd loci = the scene at that loci CaM CoMbing GuM = the object is GuM.”
By going through all of those links, I’m not sure how well you’d be connecting 73 to GuM. Over time all of that extra will fall away, but it may take quite a bit longer.
I’d try to start learning the direct associations without using a palace at first. If you are only going for 30 every few days, I think you’ll be able to make them stick. At first it will be super frustrating but every time you blank or fail a recall, you’ll be seeing the correct answer and you should use that to reinforce the connection. When Anki shows you the number again later, there will be a better chance you’ll be able to get it because with each active rep, you strengthen that direct connection until it becomes the first thing that springs to mind.