Given your situation, you might be very happy with a smaller Shop Vac, 4gallon is about the smallest, but you want to get one with a hose that matches the opening of the dust collector. In your case go for the Home Depot model with a Home Depot 5 gallon bucket. Take the lid to the dust vacs to make sure the hoses fit OK. If they're a little loose, you can use some aluminum duct tape (NOT DUCK tape) to seal them up.
If you find a used dust vac, take the hoses to HD to trial fit them.
Dust collection on CNCs generally starts with some kind of brush that surrounds the bit and just ligtly touches the surface you're cutting. The suction will pull most sawdust directly into your dust collection system. How you attach it to your CNC router so they move together is a matter of figuring something out that works. If the hose is heavy or stiff, you will need to hang it so it doesn't pull on the machine.
I've attached a pdf on making money with the CNC, and although your system is small, you may still be able to earn enough with it to upgrade over time. Take a moment to read this post onb tiny wood boxes,
https://www.routerforums.com/kp91s-gallery/140379-tiny-wood-boxes.html. You might get some ideas from that string. I'd love to have pill boxes like the ones shown.
I posted this because I was a business consultant for nearly 4 decades and I love seeing someone ambitious thriving. I also recall that at 15, I was learning skills that have stuck with me and empowered me for the past 60 years. David, by the way, is one of our resident CNC experts and over time you might ask your parents to surprise you with a couple of books by our most artistic and commercial CNC guys, who goes by
@Gaffboat around here, but Oliver is his name and his company is Prof. Henry. I posted pictures of his books, available on Amazon.
I'd show this post to my parents if I were you, so they can do whatever is necessary to help you succeed at this CNC thing. Most people are not familiar with it, but is opens a world of opportunity to anyone who is good at it. Eventually you will outgrow the amateur machines, an their support and understanding is likely to help you advance your skills and tools.
I know that our local community college has classes on CNC and maybe you could register in one of the evening classes. I am fascinated by what the CNC machines can do the opportunities they open up for users. Even if you're college bound, you could make enough with CNC to pay tuition with incurring debt.
One last thing, your parents will appreciate it that your dust collection system reduces the amount of sawdust that leaks into the house.