One thing you mentioned was navigating group buys. Those are difficult sometimes because it’s not up to us as consumers when things will go on sale. For me, I subscribe to people like Trevi_Lux MadMax and Bilakos so I can scour their pages for deals. There are others you can subscribe to and maybe some people can suggest some more since I’m not a pro. With group buys it’s not an exact science and though the price is right the shipping usually takes a month or so. Not a dealbreaker but something to keep in mind. If you don’t see the item you want on a particular site you can always direct message some of those deal people and they might be able to find you a code to use at checkout.
For quicker service try checking out MtnElectronics for well-modded lights and SUPER fast shipping. Like if you have an itch for a modded light you’ll have it in your grubby hands in 4 days tops. And that’s what he does best IMO, provides lights that are more pricey than Gearbest but quality is perfect, made in USA and shipped fast to you. Plus he can max out an ordinary light and has more options on tints, emitters etc.
For batteries I recommend Mtn Elec, Illumn, Liion, as reliable sellers. Sometimes costs a bit more than GearBest or Banggood but there’s a peace of mind that you know the batteries are good quality.
Finally let me direct you down another rabbit hole/resource in Reddit. r/flashlight is another great place to view pics and read thoughts on new flashlights and ask questions about all things flashlights. I’m not directing anyone away from BLF; it’s just another fun place to be a flashaholic. They’ve got their own feel but the sidebar is full of helpful links to help flashlight newbies and experts alike.
This forum is probably the safest place on the planet to ask anyone about flashlights, though. You can search the threads for your question to see if someone has already asked but even if you simply start a thread with your question and it’s been asked before they’ll still be super nice to you. It’s what this place does best. I’m still a noob by many standards but I’m a lot smarter because of this place. So ask away like you’ve done here and welcome!