My first manifestation was when I was about 10 or 11, perhaps a bit younger, before I knew anything about actual magic (outside of my favourite fantasy noels) or conscious manifestation 
I had robust imaginary skills as a child and I’d often be lost in daydreaming of a situation I wanted (or rather a hobby I wanted to indulge in) which was largely out of reach due to money; within a year or so, my world shifted so that I was able to participate in said hobby regularly.
A few years ago I did a similar thing when I was obsessed with a specific outcome and my entire day would be consumed with daydreaming about it. After about eight or nine months it came to fruition.
Entity-wise, I had success right off the bat with Dantalion and Sallos (about two to four weeks turnaround for both) and Belial (perhaps 3 or 4 months). 
I remember being very grateful, and both shocked but also not shocked at all when I got my results.
Edit: also, there is a similar-ish thread which some people might find of interest: