What do you mean "more speedy is more better"?
You're powering the neon off the mains right, so that means it will flash at either 100Hz or 120Hz without any special circuit, if it's running of an electronic switching ballest the it'll flash at >50kHz. Seriously what frequency do you want? fast is good if you're using if for communication flash rates in excess of 10MHz might be possible, but if you want something pretty then there's no point if it's flashing so fast you can't see it. ;D