Amity knows more about good hamster mixes in the US (I’m in the Uk). I tend to recommend Harry or Hazel Hamster as a basic for those who aren’t that experienced (and as originally they were going to a rescue so something simple and all in one). There are better mixes as you have found.
Your shopping list looks fine to me! They will love the 12” silent runner wheels. And the coconut hides. I’m not so sure about the long bridges - quite a few people do use them - usually in cages (the hooks attach to the bars). I’ve never got on with them - our hamsters were nervous as they wobbled, plus the end part can break or the hooks come unattached snd it falls down (freaked my hamster out!). I’m not sure how they would work in a bin cage.
Standard bendy bridges may be better. Or my favourite which is cork logs. They make a large tunnel and also something to climb over (or can be used as a ramp up to a shelf if next to a platform). They’re an interesting texture for them too. Some can be very large though (long) so if you do get some, shorter ones are better - nite angel may have some shorter ones.
For a bin cage, a platform snd a good sized house are important too. A shoebox house is fine. You cut the base out of a shoebox and keep the lid as a lift off roof and cut a hole for a door - ideally at one end of one of the long sides (so the other end is darker). If you then put a corner litter tray at the door end (back corner of the house) they will almost certainly use it.
Their pee is the only smelly unhygienic thing and they will pee in a litter tray if you provide one (with chinchilla bathing sand in it - which soaks up the pee). The rest of the cage stays clean and dry and you just empty the litter tray once or twice a week (hence the lift off roof on the house). The key with the litter tray is to put it where they have chosen a toilet area (usually a corner on the cage) otherwise they’ll ignore it! But I find if you provide a large house, they move their toilet area into a corner of the house - they seem to like having an en-suite bathroom! A large house/nesting box that’s dark inside helps them feel secure and have natural behaviours. Open underneath and sat directly on the substrate - so there’s room inside for them to build a large nest and they can bury their hoards under the nest, in the substrate. They tend to keep their pee away from the nest and hoard of there’s a toilet. Although younger hamsters do pee in their nest occasionally but usually grow out of it.
Hence spot cleaning. If you only need to empty the litter tray once or twice a week, the rest of the cage stays clean and dry - they are quite clean little things. So you don’t need to change the substrate that often - you can just spot clean as and when needed (ie take out a handful or two of substrate and add a new handful or two. They often follow your hand while you’re doing it, to see what you’re up to! I find the substrate flattens down over time as well so just add a bit more when it does. So doing that method I only change the substrate about every three months- and even then keep back some of the old substrate that’s clean and spread it on top of the new (smells familiar so they don’t get stressed and feel lost). That layer eventually gets spot cleaned out again
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When doing the substrate change you can clean the bottom of the bin but with a litter tray, the bottom of the cage is usually clean and dry - so just needs wiping with warm water (or warm water with a bit of dish washing liquid in - if using that don’t use anything too scented and rinse well afterwards).
They use scent to find their way around the cage and leave scent trails. Using scent and whiskers mainly to find their way about (and familiarity of objects) - hence change snd removal of scent stresses them out. They don’t see well at all!
With a large cage like you’re making, and four to six inches of substrate, the spot cleaning method works well. Avoids stressing the hamster and saves you money on substrate - in the long run - although needs quite a lot to start with.
Walmart used to sell boxo in bulk - which can work out a lot cheaper (soft cardboard substrate). Can be used on its own or mixed with Kaytee c and c to make it go further.
Platforms can be tricky to fit in a bin cage but easily made (or nite angel may sell them). It’s somewhere to go - they like to have overhead cover to feel secure so like to go under a platform and it’s something to climb onto (and a good place to put heavier items that could sink in the substrate if tunnelled under - like ceramic things - also a good place for a food bowl and another little hidey place eg.
I wouldn’t worry about one for the current bin but would be good for the ones your making (additional enrichment for when they move).