I'm not sure about HN policy here regarding linking to such things. For a couple of years I ordered from Afinil Express, who have semirecently changed their name to Shark Mood. You can guess/Google the URL. For security you'll definitely want to use cryptocurrency and not a credit card; apparently the issue is shady overseas card processors and not the merchant(s) themselves FWIW.

As far as dosage, it's really trial and error I suppose. Generally each pill is meant as a single dose AFAIK. You can always dip your toes in the water by starting off with 1/4 or 1/2 a pill.

I generally do 1/2 a pill before breakfast and 1/2 a pill before lunch (on work days) and roughly half that amount on off days.

Gf had a huge stash she ordered from India years back. I almost ran through them over the years so will need to restock but it doesn't seem as big of a deal as getting rec drugs, more like ordering steroids

It’s only schedule IV. The other stimulants are schedule II because they can be abused.