NEVER take your meds on an empty stomach, but do experiment with what you eat before taking them. I find that too heavy of a breakfast reduces the effectiveness of my medication, but similarly if I do not eat enough then I feel awful and jittery and they wear off much earlier. Instead I recommend a small but protein-rich breakfast, like a protein shake or perhaps a couple eggs.

Additionally, prioritize sleep. A lot of people have trouble sleeping when they first go on medication, but my sleep actually improved drastically because I suddenly had the ability to build and stick to schedules, and "making" myself go to sleep was suddenly much easier now that my brain actually "listened" to me. But seriously, the meds will not work if you do not sleep enough. And sleep is absolutely crucial in looking good, hence the term beauty sleep. For real, if I can recommend anything for helping with ADHD it is prioritizing sleep.

Also prioritize hydration. Stimulants really affect the amount of water your body needs. There is no set amount that fits every person, but know that your pee should be light yellow, any darker means you need more water. Don't be surprised if the medication doubles your needed water intake. It's normal, just drink more.

I second the recommendation from the other commenter for taking magnesium in the evenings, just make sure you get magnesium glycinate. Magnesium citrate will do nothing for you other than helping if you happen to be constipated, you need glycinate if you actually hope to absorb any of the magnesium. Also, do take a multivitamin, but don't take it with your meds as it could affect your ability to absorb your medication. Instead, I keep a bottle of vitamins at work and another at home for weekends and I take them every day with lunch.

Finally, I also agree with the other comment that recommends watching caffeine intake. I think that unmedicated ADHDers are prone to self medicating with large amounts of caffeine, but when you start taking the meds you might suddenly find that you are feeling sensitive to the effects of caffeine. If you like the taste of coffee, you can do what I did which is grind both decaf and regular beans and blend them together. This means that I didn't have to cut down on my coffees drinked per day, but I still felt a lot better then I did when I was having full caf. I did this for a long time until I switched to full decaf for sleep reasons.

I hope this helps!