Use 500mcg pills. It only takes around 300mcg to get the full effects of melatonin. Once you reach around 1mg, your body will quickly adapt and it will lose effectiveness.

I used 300mcg for months and months, slept better, had vivid dreams, and the effect didn't change. I switched to 500mcg pills from Trader Joe's only because the 300mcg pills stopped being carried locally.

Source: an in-depth article I read years ago that I can never seem to find.