Forum members bilakos10, Fin17, and Trevi_lux have regularly updated discount code threads. In these threads you only need to look in the most recent post to find active codes. bilakos10 codes seem to seem to be valid for quite a small number of uses so they expire quickly, but the others don’t seem to be too bad. I believe all three only get coded from GearBest.
Fin17 - GearBEST's Sale . Rovyvon A5 $15.99 . Convoy S21 $15.99
Forum member M4D M4X has a website with a list of codes. You’ll need to register and most of the codes I’ve tried had expired, but M4D M4X gets codes from Banggood.
M4D M4X website - https://m4dm4x.com
If you’re after a specific item you can ask the thread owner to request a code for it, but not all requests are granted and the discounts aren’t necessarily great.
In addition to the discount code threads, forum members often arrange group buys for specific items in their own threads.
There are some items that seem to have discount codes available almost constantly, and others for which the discount seems to fluctuate. Occasionally there are real bargains, like the golden era of the 9.99 Zanflare F1 or the recent half-price Convoy L2. Some brands are hardly ever discounted. I think it’s worth keeping an eye on the threads just to know what the real street prices of some common lights are. I’d be kicking myself if I had paid Gearbest’s full price for a Zanflare F1 or Nitecore TIP.
Some things are worth buying directly from the manufacturer. Convoys are a good example - you can get an S2+ super cheap with a code, but it will probably have the annoying old firmware and a 1A emitter. If that’s what you like or you just want a host then go for it, but if you buy directly from Convoy via AliExpress Simon can customise your light and the price is still very reasonable.