@strobberypi the hardest genres that I've seen are teen fiction and romance, followed by humor and short story and chicklit. I haven't had personal experience with fantasy, sci fi, fanfic, & werewolf, but I've heard that these are harder genres also. these genres (all that I've mentioned) are generally more popular (there are more watty winners + featured stories in these genres) than action and adventure because these are a lot more vague and not used as often in real life!
the reason why it's so much harder to climb in those is because they've got so many more stories in those genres. action and adventure don't have as many.
the algorithm is based on votes, comments, reads, and updating schedule (as far as I've seen + read). it's based off proportion (so if you get 15 reads in a day but you only had 5 total, you'll probably jump to 900s in some genres). Votes are definitely important (vote to read ratios) but reads still contribute!
hope this helps!