As a simple bulb upgrade, go to any online rally/racing shop and get a 100W H4 bulb.
DO NOT fall for any of the ones that call themselves 'Zenon' or anything similar.....they aren't Zenon, they just use the name.
Most 'superbright' 100W bulbs will do the job, but they are quite likely to damage the beam reflector and technically, they're illegal.
They also use a LOT more current than a standard H4 bulb, and despite what you may read from people who recommend so-and-so x bright version that has lasted them


years without a fault, the fact is they WILL last less time in full use than a standard bulb.
I've also no doubt that many people will tell you instantly to go for an HID kit.....the problem with that is you have an H$ bulb which uses a twin filament lamp......an HID will give you a FAR better low beam, or a FAR BETTERF dipped beam, but because of their intrinsic design, will NEVER give you a better performance in both HIGH and DIP.(look into how they work and you'll see what I mean)
The best solution, IMNSHO, is to get a brighter rally style non-farkle bulb (keeping as far away from any 'blue' 'zenon' 'Superbright' or any other fancy imagery name......and add a decent pair of 10W Cree LED lights to 'fill in' any dim places in your beam pattern, and maybe a pair of 5w floods to fill in the close up, wide pattern stuff.
Go to Halfords or anywhere online and buy a cheap pair of
'Super dooper triple bright power packed ultracool blue zenon fandango superburning' lights, and you will end up on a dark backroad with a blown bulb and we will all laugh at you
PS I mean the above sincerely.......there is an inherent problem with 'old tech' H4 bulbs that you can't really get around.........short of fitting a completely different light unit with a more modern reflector set up, you are stuck with the lesser of two weevils (sorry, I'm reading Jack Aubrey again ;BLAST)