So you're familiar with stimulant usage which means that it's going to colour your experience somewhat.

Generally when people first start on a stimulant, there's a short term experience of mild euphoria that people who are naive to stimulants don't really have a frame of reference to understand it by but that typically passes within a couple of days and I'd say at the most a week.

A pure ADHD experience of first going onto stimulants is going to vary depending on the person, their neurochemical makeup, and their response to whichever meds they get put on but AuDHD definitely complicates the experience imo. (FWIW I'm an AuDHDer on stimulant meds who has gone through nearly the entire gamut of meds prescribed for ADHD and I have a grasp of psychopharmacology, so feel free to pick my brains if you like.)

The typical experience of stimulant meds for a pure ADHDer is typically one where the person feels some brief, mild euphoria but the predominant experiences are:

• Clarity of thought
• Feeling as though your thoughts are more orderly and organised
• Increased ability for task initiation*
• Improved executive function
• Feeling like you're better able to "get through the day"
• Improved impulse control
• Typically, less "dopamine-chasing" behaviours and less compulsion for behavioural addictions (e.g. impulse buying, binge eating etc.)
• Reduced emotional reactivity

Typical side effects are:

• Decreased appetite
• Increased heart rate
• Mild insomnia
• Increased anxiety

Typically if you are on a stable dose for about a week, your side effects will settle down.

With this in mind, I would recommend staying on a stable dose for at least a week, taking it at a regular time each day, before you start forming your opinions of methylphenidate (unless the side effects are unmanageable.)

*Improved task initiation is a bit of a tricky thing to define the experience of and to identify in yourself, especially if you are late diagnosed and/or burnt out. I'll elaborate at the end of the comment.

I'm particularly sensitive to the norepinephrinergic effects of meds, and the first-line stimulants are quite strong in this respect. I had to cut out caffeine because in combination with stimulants it was causing me too many anxiety-related side effects.

Without caffeine it's much more manageable and I feel less gacked.

Taking stimulants on an empty stomach is not a good idea. Try to have something with protein in it and maybe eat before you take your stimulants, if possible. If not, smoothies or protein shakes are your friend.

According to Russell Barkley, one of the foremost experts in ADHD, methylphenidate works for about 40% of ADHDers and amphetqamine-based stimulants work for about another 40% of ADHDers (which sounds astoundingly low but that success rate is the envy of other psychiatric meds). What this means is that there's a decent chance that methylphenidate might not be the right one for you and that's okay. With this in mind, I wouldn't jump to conclusions about your ADHD status based on your initial experience of only one medication.

Within a couple of days I took it again, but being good and eating in the morning with no coffee. I couldn't even tell if it was working. I may have taken it another time soon after and did not notice a difference, so I stopped taking it.

Often the experience of stimulants meds, when they're at the right dose, is quite subtle and you may not notice the impacts it has on your behaviour but the people around you might notice improvements or you might find that there are less dishes piling up in the sink and that you're going to the gym more consistently etc.

As for task initiation, there's often a sort of lag or a "stickiness" to this for a late-diagnosed ADHDer. (If you are burnt out this is a confounding factor too.) Essentially, as an ADHDer, you have probably had to drag yourself through doing the tasks you hate and you've almost certainly built up a serious, deep-seated negative association because of a lack of dopamine. ADHD meds help with the lack of dopamine and they make starting on tasks easier however you should expect that it will be a long-term process of shifting your attitude towards those tasks that you particularly struggle with or dislike. You should find that it's easier to get started on those tasks and that you're more capable of seeing them through to the end however if the cumulative effect of literally forcing yourself to do these tasks over years and years is negative then there's going to be a significant adjustment period because your psychology won't just magically adjust instantaneously, despite your brain chemistry making things easier for you.

What this looks like in practice might be that you are still really resistant or reluctant to start on those undesirable tasks and so you continue to put them off as you did prior to being medicated but if you set your mind to it, you should find that doing those tasks feels much easier than you expected.

I'll reply in another comment about how AuDHDers tend to experience stimulant meds and how burnout and diet have an impact on what the meds do once I can muster the brainpower.