I'm new but I've worked in publishing, specifically erotic romance published online. There are general periods of the year that are good for sales (generally, around holidays because people have time off, or they're lonely and seeking distraction), and others that are not so great. The collected observations of about a decade: August-September is back-to-school season for both kids and college students, which means if your clientele includes students or parents, they've got to buy stuff in prep for the school year. If neither of those apply to your audience, then it's a pretty decent month. October is generally a decent month, with people gearing up for Halloween.
November and December are either slow-downs because people are buying gifts for friends and family, OR they're massively successful because people that don't have as many obligations will treat themselves (and others that they feel close to). I suspect this is where a camgirl could shine knowing how to work the right audience. Also, there's student break for the holidays, which could be good or bad depending on your clientele. A grad student living on his own (most likely with roomies) is going to likely have more time than a father whose kid/s are now home for college break or on K-12 break. There are other factors but basically this is where you need to know your audience.
Aside from the obvious holiday of NYE/NY, January either slows down or shows an increase. This is because the holiday stress is finally past and people can relax, plus they've got new toys from Xmas to play with, and maybe some gift money to spend. Give a reason to spend it on you.
With the exception of Valentine's Day, February tends to suck for lots of different markets. It's part of why Deadpool and Black Panther's box office successes in February were taken as such a shock by the industry (because while there was a lot of advance audience hype, on paper, an R-rated superhero movie and an entirely black-led and cast superhero movie taking place in a fictional hyper-civilization in Africa were major risks because they hadn't been done before). February is a glum, drab, and a lot of people struggle with seasonal depression.
March is the beginning of spring, and things start to pick up a little here (although it's usually still a little slow, recovering from February) and in April. There's spring break, There are some religious holidays but they're not so much part of the dominant culture that they have a major impact. You do an egg painting show for Easter, maybe? (Although, that usually ends up with me painting myself, because I fail at dyeing eggs.)
May tends to be an okay month, but as soon as school lets out in either May or June (depending on location), and summer starts, expect things to slow down. The reason here is there's just too much competition in summer. The weather is either lovely or trying to kill you, people who can do so like to do stuff outside, this is a popular time to travel, summers are usually filled with blockbuster movie releases, students are out of school (both adults and kids), and there's just so much going on that people have to prioritize. There are things that you can do to help remind your clients that you exist, but only if they also follow you on social media. They just may not have the time, the energy, or the money, though.
Hopefully this is helpful. Again, this is based on observations in selling other sexual content, and the audience does differ (erotic romance novels are mostly popular with middle-aged women, particularly educated moms), so I made adjustments as to where it would be likely to differ based on the sort of audience that camgirls tend to attract (mostly, it seems, lonely or horny guys of varying ages).