This is simple but interesting question, and so I'll give as straight of an answer as I can. The most honest answer I can give is that when it comes to dating, yes, looks matter massively. People often say things such as "first impressions matter", but don't then make the connection that a lot of what makes up a first impression is how you look at first sight. When teenagers start dating, looks matter even more than they do already, this is just a simple fact that can't be avoided.
There's a reason why I have to be so blunt, and that is because if I told you it was mostly because of personality, and you then failed to get a date, you'd assume you were doing something wrong or your personality was bad, when it might not be. If that was the case, then this could really hurt you in the long term and constantly make you feel like you were doing something wrong, which would be extremely stressful.
The good news is that when it comes to making friends, looks still matter, but they're not nearly as important. You can actually make a lot of friends by being funny, making good conversation etc, even if you're not very good looking.
I noticed you talked about how you had improved your personality, and were looking to improve your looks, so I guess I'll give some advice on that. Make sure to shave often, because scraggly facial hair is unattractive. If you have a monobrow like I used to, pluck it out, don't shave it. If you have acne, use cream for it. You said you hated your body, if it's because you're overweight I recommend running, not only because it is a great way to get slimmer but also because I personally enjoy it. Something I realised only recently is that the glasses you wear, if any, are extremely important, and personally I'll probably be switching to contact lenses soon because of this.
The best advice I can give you is to do what I listed above to improve your looks and make decent fashion choices. Dating as a young man if you're not good looking can be rough, stay strong and try and be confident.