Wait until you read on these forums that Tesla has opened up new enrollments for FSDb again before you subscribe. Since you are on 12.5.3, you will not get FSDb 11.4.x because it is being released on 2023.6.x, which is older than what you currently have. So, in addition to waiting for Tesla to accept new testers, you also need to wait until FSD is released against a new version of software than what you have. This is because Tesla DOES NOT roll back to older software.yeah shame on me... I listen to the ride the lightning pod cast weekly and I heard months ago that they had stopped making people get a good safety score to get FSD... my understanding was all you had to do was pay for it.... and you could pay monthly or all at once. I wanted to dip my toe in to see how it worked before ponying up $9000 more.
The most common advice given here is to stop installing software updates until FSDb passes up your current version. Your car will automatically download new software as it becomes available, but you should NOT install it. FSDb is almost always behind the main production software except for the holiday release, so, if you keep installing new software, the only opportunity you will ever have to get FSDb is at the end of the year, and maybe not even then, depending on how Tesla sequences the rollouts.
So, save your money and cancel your subscription to FSD until your software is older than the FSD software release AND you see that Tesla is adding new testers to FSDb.