As a fellow teen, (I assume, at least), I would suggest finding a way to earn the money yourself to prove to your dad you care enough about having a chess membership to work for it. Also, make sure to bring the subject to him when he is in a good mood. (I find my dad is most susceptible after a New York Rangers win heh)
How to convince my dad to get me chess.com diamond?

I want to dedicate myself to being a better chess, player, doing more lessons and games review and learning from my mistakes. But my dad doesn't want to get it cuz it's "Too expensive". How do I convince him? I was thinking do the free trial and show him all the stuff I get and show him how much chess I'm gonna play (A lot) but I'm open to any other suggestions
If you truly dedicate yourself to chess, i.e. spend more than an hour day studying (not just playing blitz or using the forums), and do this consistently, for say a couple of months, then you'll show that you're truly serious about chess, and not just here to use these forums as surrogate TikTok, which might make him may reconsider.
Of course, this depends on your family's financial situation, but your dad probably does have the money to pay for the membership; he simply does not want to pay the money for a membership that (in his view) you won't put to good use.
Personally, I think that the diamond membership is a scam, when there are so many free resources online, but what do I know? Perhaps people really are getting something out of the chess.com lessons.
you aren't really helping him with that long paragraph...
Just because you have a 15 second attention span does not mean that everyone else does. I'm not writing for the lowest common denominator.
and how does that apply to attention span?
Well, the fact that you're not even capable of writing a full sentence, is more than enough proof of the aforementioned statement.
Honestly, I don't get any enjoyment out of bullying 9 year olds, but if you're going to criticize my comment as being "too long" for your attention span, then I think that I have a right to respond.
I am fully capable of writing full sentences, I just don't think you're worth that much of my time. I'm glad you find yourself so intelligent, but I hope you realize you're just a pretentious child.

I am fully capable of writing full sentences, I just don't think you're worth that much of my time. I'm glad you find yourself so intelligent, but I hope you realize you're just a pretentious child.
Nice try, but you still have some things to work on. Simply calling someone a "child" and "pretentious" is not very insulting. You have to be subtler.

Try using a free daily chess.com lesson to show you will use the membership, and maybe show him if you are annoyed only having 1 lesson per day, or show him the great features of game review ad how fun puzzles are.

I want to dedicate myself to being a better chess, player, doing more lessons and games review and learning from my mistakes. But my dad doesn't want to get it cuz it's "Too expensive". How do I convince him? I was thinking do the free trial and show him all the stuff I get and show him how much chess I'm gonna play (A lot) but I'm open to any other suggestions
If you truly dedicate yourself to chess, i.e. spend more than an hour day studying (not just playing blitz or using the forums), and do this consistently, for say a couple of months, then you'll show that you're truly serious about chess, and not just here to use these forums as surrogate TikTok, which might make him may reconsider.
Of course, this depends on your family's financial situation, but your dad probably does have the money to pay for the membership; he simply does not want to pay the money for a membership that (in his view) you won't put to good use.
Personally, I think that the diamond membership is a scam, when there are so many free resources online, but what do I know? Perhaps people really are getting something out of the chess.com lessons.
you aren't really helping him with that long paragraph...
Just because you have a 15 second attention span does not mean that everyone else does. I'm not writing for the lowest common denominator.
and how does that apply to attention span?
I don't use tiktok. I'm assuming you guys just are annoyed by the kids that do.

Only @Ziryab mentioned good grades. I can't help but wonder how so. In what world are you guys living in where rewards and good work are no longer linked to each other? Of course having good grades at school is the first and most important trick, that should get one anything from their parents, provided they can afford it.

I'm sure the main feature of a membership is free game analysis, which can be done free on other sites. No membership is needed.

I'm sure the main feature of a membership is free game analysis, which can be done free on other sites. No membership is needed.
No. There's a lot more than that. Unlimited tactics. Videos. No limits of lessons. Full access to all aspects of the site.
Yes, there are plenty of free resources on the internet, too. Some is as good as what chessdotcom offers. Some might be better. Nonetheless, chessdotcom offers quite a bit for the money if a young player will actually use it.

Hey @Toad_Red! We'd LOVE to give you a free month. I'm messaging you so you can have your dad contact us to give us permission! Check your messages!

It's good to see that chess.com now offered you a free 1 month membership, you can try it out, enjoy the perks, and then continue it if your father allows you to, but out of curiosity, I have this question: which feature(s) of chess.com do you really require desperately, which are premium only? Asking because I have made most of my improvement without a membership and could suggest some alternate ways to improve in certain areas, so do message me if your father unfortunately doesn't agree to get you a membership, although I sincerely hope he does! Good luck!
Sure, I'll try and get a job this summer, and see if my dad will at least get me platinum for now. Thanks!
glad you've figured it out!