Cyproterone is really powerful and it has a half-life of 40hours so it can be taken at a low dose daily or a mid to high dose every second day, also considering it's half-life (or how long it is active) if your on a mid to high level dose and taking it every day the strength will double up, meaning it will most definitely decrease libido and cause loss of erection completely, so if that is not good for you, you will only need a really low dose daily, or a mid to high dose every second day.
Personally I prefer bicalutamide or flutamide if I'm low on money, because it blocks the actions of testosterone instead of stopping testosterone from being made and with that being said it's much easier to find the sweet spot (or dose) that will allow me to still have erections.
Always always do HRT under medical supervision and if you're buying online always notify you're doctor on your purchase n intent of use, doctors are also required by law not to share, but to protect your medical information, your GP should also be able to refer you to other doctors to monitor your progress, if not get a new GP till you find one that will help, also if you self medicate it may effect your chances of a therapist giving you a letter of recommendation for any future surgery like ffs and srs.
I hope this helps.
