No use beating yourself up, when you were 24/25 you wanted to do the things that the young people do I'm sure. Who's to say that wasn't better.
You should start working swiftly towards getting a good GMAT score and get a tutor form a study group put together a massive action plan for that.
Work on your profile ( to the extent you can within a matter of months) and apply in the fall. There might be a slightly lesser chance that you will get into Harvard or Stanford but only slightly and otherwise you're pretty much in the right Zone.
Starting at 30 is OK. In Europe and UK the average age for MBA students is 30.
So make tracks but put all of this to the side honestly it's only going to drag you down and it's a not a deal-breaker...so just move quickly you don't have time to waste.
I think that you should get individual and group help with the GMAT and I think you should get individual and group help with the application process. Meaning that you should be efficient with your time.
https://mbaprepcoach.com