If you’ve looked at SHARP then you know 5 is the highest standard, but fit is as important if not more so, a 3 star that fits is better than a 5 that doesn’t, different makes have different fits, my advice is find a shop that has a large selection and see what make fits.
I’ve had motorbikes and fallen of bikes, helmet protects head but gloves protect your hands if you fall off at low speed and slide, jacket and trousers too, don’t need to spend a fortune but don’t scrimp either.
Also and I may be wrong but to me a 125 is a better start, it gives a bit of get out the way speed a 50 won’t. Again I could be wrong.