When I was a kid, I prayed to Aphrodite to bring me a love, but I didn’t really believe it would work, so it didn’t.
As a teen, I was a Wiccan & had good, fast results with spells. I made a sachet (not really a mojo bag, just a little herbal pillow I made & embroidered) to meet my favorite band & it was timed to the first concert I went to. I didn’t believe enough & didn’t ask for as much as I wanted. I believe that’s why I only met 2 of the 4 band members after the show. I also had mundane knowledge of where they were staying & when they usually would come to meet fans, so that helped.
Another time, in high school, I did a love spell & the flame in the cauldron shot up 2 feet or more & burned the ceiling. I did the spell before school & it worked by the time I got there. A guy that was only mildly interested in me suddenly found me fascinating & followed me around like a puppy dog. It freaked me out (& I liked him less this way), so I “undid” the spell, so to speak & he ended up hating me & that was pretty quick, too.
I’d say intent & belief are very important to making magick work & making it work quickly. But it also probably depends on what kind of magic you do.