For everyday riding and potentially getting done at night;
Trustfire D2R - gopro style mount, cheap, bright enough. I keep an extra in my pocket sometimes just in case as they are small and easy to swap while moving. Its light enough I never worry about it being mounted below my bike computer on an out front mount.
https://www.aliexpress.us/item/3256806529223121.htmlIf I know i'm going to be all alone or out in the dark for hours;
5 led, 8000mah light bar - Its not 5200lm, but its nearly on par with big outbound lights at 10% of the price. (I use this light bar for the weekly night time MTB group rides mostly, but it works great on the yearly night time gravel race i attend as well) Low beam is slightly brighter than my trustfire light and it will run most of the night on that, I just flip it between high and low depending on group position/traffic on gravel/road) I actually have 3 of these, 2 of the biggest and one of the smallest.
https://www.aliexpress.us/item/3256806810431448.htmlI never felt a need for a helmet light on gravel, on MTB or racing motorcyles, they are very important due to steep terrain, turns, and speeds.
This is the helmet light I use currently for MTB, It's kind of heavy, but I haven't found anything cheap with a remote/wired battery that doesn't disappear in the wake of my light bar.
https://www.aliexpress.us/item/3256808935404280.html(This would probably be a great bar mounted light on a gravel bike, its got a gopro mount and a remote button)
I made an imgur post of all the cheap lights i've used over the years because I see this question so often;
https://imgur.com/a/cheap-lights-that-work-81mEKUhI actually just ordered a Thumper Jockey Viking helmet light. It's been floating around $150 for years but recently dropped to $70. Its 4000Lm and has a wired battery. I don't particularly like being tethered but I had to give it a shot, maybe it won't disappear in the wake of my bicycle light bar. I'm sure it will still disappear against my motorcycle light bar, but that is a 12" 6200Lm bar that I can barely outrun at 60-70mph in the desert.
https://www.thumperjockey.com/#!/Viking-Helmet-Light/p/556764418