I've used A1 Mini with:
All screws are M5. Some parts of ladder which have thicker spacers demands atleast 25mm of length, so I'd advice you to buy some M5 30mm
But how many?
Depends on the amount of ladders you'll put, and it depends how you set it up - just take a look at image and count how many you'll need depending on how tall it's gonna be, mine uses 32x M5x30mm
Tank
Well, if you're from Poland there's link where I bought it https://allegro.pl/oferta/terdens-sloik-pojemnik-plastikowy-na-ogorki-3-l-15693605824
I guess you'll find it on amazon / allie too, or just find something what will fit the main screw of my design which is around 123mm (+ screw)
Well, I've never worked at IKEA, so you have to enjoy this picture
The amount of ladders you'll print depends on you, these which I showed seems like maximum, but who knows ;)
The author marked this model as their own original creation.