There are directions for the Fuji kit in the FAQ in my signature.

Yes, you can definitely make up smaller quantities. I typically make up 1L (16 rolls worth) at a time from the Fuji kit. Obviously you would use 1/5 of each concentrate to make each litre. Don't try to store the concentrates in the original bottles because the caps, once opened, are NOT airtight. You need to transfer the concentrates to glass bottles with a good seal and exclude ALL air using butane. You can store the developer working-solution in the fridge for many months in PET bottles, again with absolutely no air permitted. Fix and bleach can sit on the shelf happily; they don't really go off.

The other thing is that the bleach and fixer have 2-3x the life of the developer, so what I do is:
- make up 1L of everything
- soup 16 rolls then discard developer
- make up 1L of developer
- soup 16 rolls then discard developer
- make up 1L of developer
- soup 16 rolls then discard developer
- send fixer off for silver reclamation, store the bleach until you can buy regenerator
- make up another 1L of everything
- keep going until all developer is used up...

At that point, you have lots of spare bleach and fix, the bleach being the most expensive part of the chemistry by far. You can now buy some more developer cheaply and use it with your old bleach+fix.

Remember to aerate the bleach (shake it in a half-full bottle vigorously) before each use. Oxygenating the bleach will restore much of its activity. Once you've put about 50 rolls per litre through the bleach (3x the capacity of the developer), you can buy "Bleach Regenerator" that will extend its life even further. I bought two of the 5L kits (160 rolls worth of developer and about 500 rolls worth of bleach before regeneration) so I haven't gotten to that point yet.

Don't put bleach or fix down the drain. Exhausted fixer can be donated to a photo lab who will reclaim the silver from it; bleach should be taken to a HAZMAT disposal location or the lab might be generous and take it from you at the same time as your fixer. Developer can go down the drain highly diluted, e.g. 10+1.