If they don’t exist, how much of a disadvantage will I be at when trying to improve my memorisation?
Thanks
Visualization will improve with practice. Everyone here started not knowing a thing about memory techniques and many of us claimed to be bad at visualizing. You simply have to dive in and start trying.
To answer your question though, many folks use people to represent their numbers and cards. So for events like random digits, binary digits, playing cards, using a system constructed with the Major System, Dominic System, or even Category system, you can use all people instead of objects.
Now, as to visualizing locations…again, it will get better with practice. But you don’t have to be able to see every detail of a locus for it to be useful in memorizing. I have a lot of memory palaces where the exact appearance of loci are a little hazy, but they still work for me in memorizing. But if you decide you just can’t use the Method of Loci (or more likely, don’t want to) you can use a Peg System or the Story method.
Ah, ok. I guess I’ll just get started then 
I concur. Meditation is a biggy and most people negate it.