Now when you say "magic" I assume you don't mean stage tricks and illusions, as there is actually a difference. Using the word Magick is referring to sorcery and energy manipulation.
Magick is an attempt to manipulate others & reality itself through your "subconscious". Intent. Will. There's some practitioners that say you must "Believe" in what your casting in, in order for it to work. There's others that say it's okay to be passive about it when your casting a spell since it will work anyways. But most if not all practitioners agree that when your doing energy work, you have to put your HEART into it!
As for Magick being "everything" added with what's not explained by science yet, I'd say about 50/50 if you try to look at it through that lens. The same way money makes this world go round, is the same way Magick makes this universe go around. Minds have more significance then Materialism and New Age will allow it. It's so much more then "mental imprinting". Your heart & commitment needs to be put into it, not your "belief".
As for the dream spell you mentioned I will share my experience to give you an idea. After an emotional crisis that happened to me 2 years back that "grounded" me into this world, and completely blocked me off from spiritually advancing, I couldn't dream, I couldn't meditate, I couldnt ap/obe, I couldn't do anything. Every night was dreamless, and even when I did dream, it was nothing significant as it was nothing besides subconscious "Fluff" replaying itself. My girlfriends uncle is a practitioner in Santeria, and he knew about my personal problems, as it was also hindering my will to advance. No techniques I've read online could help me, I was far past that point. He made a small sachet for me, mixed with Oil & herbs, It took a few hours for him to make and cast. He said It will help me induce lucid dreams If I smell into the sachet every night right before I go to bed. I wasn't skeptical about it but neither was I entirely open. He didnt give me a time frame either he just said to "Do it".
One night before I go to bed I inhale the strong scents deeply, and lay down and rest.. 1st night I didnt feel a difference.. 2nd Night I do it again, I start getting small dreams again that seem like something more then my "subconscious" replaying stuff about ordinary life. As I started to do it more and more, I didn't start lucid dreaming yet, But I found my Dream memory recall was improving. Not only did I remember my dreams in almost full detail, The dreams themselves started becoming more crisp, more vibrant, more vividness, more sharpness, and added depth to it, shortly overtime until finally, I broke the barrier where my "awareness" made it through, and I started to induce lucid dreams again, on my own.
The way magick works is not always about having instant results, It's about making an outcome happen through non-physical means. The non-physical will use the physical as "tools" and carve a pathway for you in order to get your will to be done. New Age will tell you stuff like it's all "inside" your head", Or as they would say "believe" and you will make it "real", but as I said It's so much more then that. When you evoke energies, They are DEFINITELY outside you, you need to train yourself to sense and manipulate energies.
Magick is not an instant miracle but a tool both to aide and improve your life. It will not work if you put out negative energy in regards to it's manifestation. Your doubt and negativity can actually negate and nullify the magick from working either that or it will backfire.
A Gambling Spell will not make you win EVERY time but it will help you win MORE. A Weight Loss Spell will not work if you sit on the couch eating 'Bon-Bons'(or Snickers, Ice Cream, Pasta, etc...) every day, all day long but it will alter your metabolism, give you increased will power and thus faster weight loss if you try.
You must work WITH your chosen Spell(s) to bring about the most positive and effective manifestation. Watch for signs and follow them, take advantage of the opportunities placed before you by the Forces of Magick and manipulations of energetic intent.
Finally, if your still skeptical about Magick, It wouldn't hurt to do a little more research on the subject as they are many systems and methods, also you should probably seek out a few "occult" forums to have your questions answered by people who actually do practice these concepts for a living and make it their life..
Hope this helps.