Hi Thor
If you do a fishless cycle, you can get everything but the otos - assuming you can find a shop that will sell you that many fish in one go. Or go to a few shops. However, it may be worth waiting a few weeks before getting cories as some species can be a bit delicate.
Otos need to wait until the tank has grown a fair amount of algae or they are very likely to die. And when you do buy them, if possible wait until they've been in the shop a couple of weeks (so the weak ones will already have died) and choose the ones with fat bellies are they are eating well.
As for numbers, if you have an external filter you could easily accommodate shoals of 10 each of the barbs, tetras, cories and loaches, with half a dozen loaches and eventually half a dozen otos. The community creator on here puts that at just 62% stocked meaning you could have even bigger shoals or perhaps a single/pair/trio of centrepiece fish.
If you have an internal, then stick to shoals of 6 for each species, which would give you 78% stocked when you finally get the otos.
If you intend doing a fish-in cycle, then I would suggest the barbs or harlequins from your list to start with. But doing a fishless cycle would be a lot easier and allow you to fully stock your tank a lot faster.
