This question has been asked before. There was once a member here who wanted to turn some Instagram model into his personal sex slave, even though she lived 2000 miles from him, and had absolutely no knowledge of his existence.
There was another who wanted to get the attention of a famous boxer to train him, but, of course, the boxer didn’t even know who he was and they weren’t even in the same state.
Magick is limitless, but, unfortunately, few magicians are.
There is this little something called your Sphere of Influence. The idea is mainly used in Law of Attraction circles but I have found it to have a lot of relevance in magick too (after all, what is LOA but the watered down principles of the Kybalion?)
What the Sphere of Influence means, is that it is easier to attract something or someone around you, then someone or something that is beyond your current level of belief
For example, if you are living on the street, your magick has a much greater probability of being successful if you enchant for a bed at a local shelter, than if you cast a spell to get a room at the fanciest hotel in town. If you are financially strapped, it is easier to conjure up some extra employment opportunities than a lottery win. It is more successful to do a spell to bang the girl next door, than a famous Hollywood actress who doesn’t live anywhere near you and has never even heard of you before.
Now, these things can, eventually, be done, but only if you have practiced long enough to increase your Sphere of Influence and your level of belief. There is a reason why in both magick and LOA beginners are told to start small. It increases confidence in the powers and each success widens the Sphere of Influence to encompass greater and greater possibilities.
Having grandiose ideas of what magic can do for you is all well and good, but why go after something with such a high level of improbability and a greater chance of failure? Celebrities are notoriously hard to influence, second only to politicians, and if you don’t live in their neck of the woods, getting them to notice you is very improbable, simply because there are a lot of people vying for their attention (most celebrities that marry “normal” people tend to meet them in places where the celebrity goes to escape from those that want their attention).
As for the idea of sending the target a memorable dream, sure, that is quite feasible, as dreams are not affected by one’s Sphere of Influence. However, it is important to point out that most people do not pay attention to their dreams, or even remember them come morning, so a dream is extremely unlikely to influence the celebrity target in any major way. If you were to encounter them in the material world, even if they were to think you looked familiar, that will not necessarily translate to them thinking anything more about it. After all, how many times do you see people on the street every day that look familiar and remind you of someone? It is a peculiar quirk of the human mind that happens all the time.
The best way to go about the goal, in my opinion, would be in stages. First, do a spell to meet the celebrity target. A Spare style Chaos sigil is good for this, as it uses your own subconscious mind to move you to the right place at the right time. Once you meet them, then do a spell to have them dream about you. In order to make it stick, though, you would have to be within proximity to them so they can encounter you again in the “real” world. If you do that twice, to three times, it will leave a lasting impression on them, and they will then try to figure out how to reach out to you themselves.