I'm going to go into this with the assumption that I have every possible resource at my disposal.
My first option would be a lethal dose under anaesthesia. This is the best method for literally everyone besides those who want to suffer through pain as they die. There isn't another way of putting this, to be honest. It's as close to peace as you will receive from death, even if it requires the 'you' part to not be functional or aware.
The second option would be a lethal dose not under anaesthesia. This is the most realistic method for those who have a small fortune sitting in their bank account, and by small, I only mean a couple thousand. The key ingredient here is the opiate. Morphine, fentanyl, heroin, all will work, given we're working with the idea that I own all required parts. If we're going off of limitations, morphine will be the easiest to receive, but some might find it easier to get heroin and fent from a contact. From there, gather a large but not overwhelming amount of alcohol - perhaps enough to fill a small glass, of 80-proof (vodka will do here, but more realistically sake would work, plus I love that stuff anyways
) - as well as an antiemetic, and a benzodiazepine of your choice. Do not be lenient with dosages. This is the most peaceful way to pass consciously. Your high would cancel out your worries and you would pass out before dying. Your CNS and respiratory system would depress, and you would eventually stop breathing and asphyxiate a while after you fell asleep. It's slow but not painful - I liken it to the last waking moments on a death bed as you die from natural causes.
It should be noted that, should anyone attempt the second option, you must be aware of bioavailability of opiod/ates and you must be quite generous. The lethal doses vary heavily between classifications and even within the classes of drugs. Some may be feasible orally, some may not.
The third, fourth and fifth options, I could not rank correctly or with great certainty as I personally know nothing of them - the only two I am keenly aware of and know lots about the process of are the two you see above. I would, however, stick the usage of sodium thiopental (commonly used for euthanasia), pentobarbital, and basically any other barbiturate in those positions. If I had to stick them all under one roof, however, they would be third, and so for the fourth I would say sodium nitrite (NaNo technique) and fifth would be inhalation of helium, carbon monoxide, or nitrogen. Fourth and fifth may be interchangeable.
You will see that almost all of these, if not all, require chemicals and substances. This is because they are the only truly peaceful way to go. Any physical method requires either the complete annihilation of the capacity of your body to function or will require such grievous pain that your brain ceases function of its own accord. In many instances, both states are to occur.
