I want to buy Against the Storm.

I could buy from Gog for $15 plus $10 for expansion.

But with key reseller sites I could get it for like $3-4 I looked at a bunch of key reseller sites with the help of chitchat and it said there was some that were reasonably reliable/trustworthy. Unfortunately my PC crashed and I lost a bunch of progress, I am not sure which one was suppose to be most trustworthy while still offering a bargain.

What are peoples opinions on this? Is buying from Steam because "DRM" that much more risky? What do people think Valve would do if they knew they were going out of business as far as patches with Steam? What key reseller sites do people trust the most?

Not a single key reseller is trustworthy, especially when it comes to GOG keys, as those keys almost always originate from non-official sources. There is a real risk that the keys you find there are linked to activities like laundering stolen credit cards, which remains a problem. So, by using these sites, you're potentially supporting criminal activity and helping keep those channels alive. You're also risking getting a key that will be revoked, due to falling victim to a scam as well. Ask yourself - what is the reason key resellers can sell a game so cheap?

In addition, if you want to support the developers who actually make the games, remember that they don’t see a single cent from sales on key reselling sites. The money goes to the marketplace and the individual sellers. A few years ago, Mike Rose from No More Robots famously said that he would rather people pirate his games than buy from key resellers, because piracy (while still illegal) does less harm to the industry than these grey-market sales.

So like Humble Bundle or Greenman which I've heard from a few sources is trustworthy, even them you would find scummy whether it be Gog or Steam keys?

No, they are both offical and verified stores, neither of them are key resellers, so they are fine. It is only the key resellers that are always dubious. Humble is also one of the few stores where you can buy GOG keys outside GOG itself.

Don;t they have to be reselling keys in order to sell Steam or GoG games, being they aren't Steam or Gog? Especially if some extra discounts are involved. Selling someone elses product is literally reselling a product. How do I determine if a site is a "official and verified store" or a "reseller"?

Other things to factor in. If I bought the game directly from Steam, it would be a little cheaper (like $5~?) to buy the game+expansion+supporter pack from Steam since Steam has a bundle with supporter pack. Of course that's if I even want the supporter pack. Not sure if I do, never used that stuff before that I recall but maybe I am missing out.

Gog does not seem to have a bundle for this game with expansions, I'd have to buy each component separately.. Additionally Steam can have larger game bundles and even if I just buy the game by itself now the larger bundles take that into account and discount the bundle accordingly,

Another option is getting the game from Epic Games, If I wanted till their black friday/holiday stuff where they have things like $5 off coupons if a game is over a certain price and such. I might save more than Gog or Steam. EG isn't evil, is it? Might I have trouble playing the game offline with EG or if EG went down losing my game access. But on the other hand buying from EG means more money goes to devs, right?

There is also a chance while I wait for there to be a extra discount sale code emailed from Gog. Though it's just a few games here and there, odds of it being for the game I want might be pretty slim.

A minor fact to figure in is that I've already played Against the Storm demo for awhile and you can seamlessly transfer your demo progress to full game I hear. Tough I believe I could just fish out the Save file from my Heroic install and move it to Steam or EG install. On the flip side finding things like Save files with Heroic especially installed via Flatpak can be extra tricky but I should be able to do it.

Yet another factor to consider is that Steam makes it much easier to view and install/uninstall mods with their workshop. Unaware if Against the storm has mods worth using or not..

Resellers (a.k.a. keyshops) are ones where people literally buy a gift code on a legit store (or get one for free, or as part of a subscription, etc.), then sell that [hopefully] unused code. Stores like Humble and Fanatical have deals with the store that they're selling codes for, and/or with the dev/pub (depends on how generating codes works for a given originating store). The latter kind likely don't even have the code generated (in cases where there even is a redemption code generated at all -- some might require account linking) until a given purchase is made (again, depending on the store the code is for). Those are okay -- at least in terms of "Does this potentially support fraudsters and other criminals?" and "Is this copy likely to be revoked from my library later?". Kinguin, G2A, and other gray-market resellers/keyshops are the ones to watch out for.
When in doubt, check a site like IsThereAnyDeal or GG.Deals to see what's on sale where. ITAD doesn't seem to even track prices for key resellers (...anymore?), while GG.Deals has "Keyshops" clearly separated from the "Official Stores" in the "Stores" dropdown filter on their search page.

The entire point of supporter packs is that they're filled with stuff you don't need, and they're only provided for people who love a game so much that they want to support the developers with extra money. If that's your goal, you should buy the game full price, or at least just buy at current price at a store with values you support. Trying to get the very best deal on something which includes a supporter pack feels very tangled to me. Having done this just two weeks ago (for a demo game played half a year ago), both on GOG, I can confirm. It's not even "you can" - it just happens automatically. Really nice.

One final note: There's enough gameplay in the base game that you're not going to get bored anytime soon. Frogs won't even show up once you reach level 9 (which takes a seriously long time of playing; I think I've put some 40 hours in (could be off there), an am currently at level 8.) So you could just get the base game, and wait for the next sale (and possibly a higher discount) before getting the expansion.

Was that Flatpak heroic installed? There is a chance for it to be a bit different for me. Well regardless it shouldn't be too hard to pull a save over and wouldn't be the worst if I had to start over. I played the demo in a certain way because of the restrictions and because I knew I could only play one cycle. It's hard to judge from the demo since it's the same forest type map over and over, so you're saying it finds new ways of keeping you interested?

No, vanilla wine. Yes. There are (obviously) different difficulty levels (viceroy can be brutal, and will really make you pay attention to details that are insignificant on lower difficulties), different mixes of races which strongly suggest different focuses and thus different playstyles (e.g. foxes have very low base comfort, but get comfort from working on glade events, so during mid-game storms, you really want as many of them as possible to be busy on such), an ever increasing number of new buildings (a map where you randomly don't get any improved way to craft planks will make you really re-evaluate what type of buildings you're building), the perks, cornerstones and orders mix things up a lot too, the different biomes do a lot for resources and atmosphere, and of course each map has its own forest mysteries - but primarily the world map has global events and modifiers, and those latter are really the thing to seek out for completely new challenges. (E.g. no trading, smaller hearth radius, an existing "mismanaged" town to take over, etc, etc.)

I played about ten towns to reforge two seals (which present a significant step up in challenge), and none of those towns were boring, while only the first few were "similar". Now I'm taking a breather, but that's because I can only ever do city building in short stretches, not because the game has run out of new challenges.

Isn't there more to the expansion than just the frogs? Why is that?

When would the next sale for something like this likely be?

Not long. It's on sale "regularly" (9-19 times in the last year). Digging into the database, I count 18 times in the last 12 months for the base game. (I guess I should expose that in the front-end, too, somehow.)

OK I bought the full game, using Heroic. My Against the storm Demo has not turned into the full game. Now what? Install the full game and uninstall demo?

Install the full game, yes. That's the only thing I did.