I don't think I ever got around to posting the MS Paint Edit that I did for this, which works as kind of like symbolism I guess?I always envisioned Wario as starting out as a dweeby loser who didn't really have much of anything to do with Mario, very insecure and kind of lacking in stamina (note how slowly he gets around in Wario Land 1; that's him pacing himself-- energy conservation).
Personally, I like to think that Wario is just some street rat that grew up picking pockets an' stuff (and that's where the greed and gluttony come from, in addition to Wario already liking the stuff-- a heart once starved, and all that). He didn't have anything at all going for him, really, no purpose in life, a real nobody with no interests other than food and money because he was an urchin. (Note: I personally discount his appearance in Yoshi's Island DS as being canon, because it's just a remake of an established title and only included the extra children as gimmicks. In other words, SMW2: Yoshi's Island is canon, Yoshi DS is not. So when I say that we don't know anything of Wario's past, I mean it's completely shrouded in mystery. As far as I'm concerned, Wario is a name that he took for himself, to distinguish that he was kinda Mario but at the same time "fuck that guy, I'm-a WAARIO." Because really, let's be honest, that's the kind of name you come up with for yourself, not one that you'd force on your children, because at least it's you that suffers from any teasing and not someone else. I wouldn't in a million years name my kid "Tahu" or "Pokey" but for me it'd be an absolute joy to throw the name around and be referred to by, and it's probably the same deal for Wario.)
This is about as far as I can explain without going to an even more considerable amount of detail: it'd take a while to be able to truly articulate my position, and as you can see, this disjointed ramble is the best I can do with whatever amount of time, but I'll try to summarize.
Little Orphan Street Waat sees a whole bunch of Mario stuff everywhere around the time of Mario Bros. 2 or smth, is like "hey I kinda resemble this guy," and decides to copy his every move so maybe he can end up in the same place; insecure cuteass humble beginnings Wario finds himself, starts to develop as a person through the interactions he'd never had the chance to have before then, due to always needing to hide away-- love of food and money comes from being a penniless starving child nobody, everybody who knew him was kind of nyehhh towards due to his larger size, and perceived 'unhinged dullard' status as a result of his cock-eye and habitual fixed grin.
Since nobody gave a shit about him, he kind of had to teach himself damn-near everything, and since he'd always been seen as an idiot, in true WAArio fighting spirit, became this scholarly-ass man that we see in his earliest appearances. Of course, since knowledge and cunning was all that he had, he was kind of boring and a nuisance to everybody that interacted with him, which only made him irritated and disheartened, and all the more determined to be a part of their lives. That is, until the events of Wario Land occur-- suddenly, a whole new world opened up to Wario, and all of a sudden, he was starting to do his own things. Instead of competing with Mario to try to buy Peach some Samus doll, he fucked off to some forest and conquered the whole damn territory... granted, not hard to do when there's only like three people in it.
From there, he continued to experiment in different venues (see Wario Blast and the aforementioned Wario's Woods) before getting his shit stolen from Captain Syrup, and the ensuing adventure caused him to 1) settle on his passion: treasure hunting and exploration and 2) (eventually) develop a taste for short-sleeved shirts. At some point after the adventure, he decided to do something about his shitty stamina, and thus took up weight lifting, and because he's-a gotta show off those sick pythons, he started wearing t-shirts more often than the usual yellow cardigan. His intellect would disappear from his speech (a compensatory tactic to offset his goofy appearance, no doubt), instead being funneled into learning how to program.
He eventually sees some incredibly gaunt man at some point while strolling through town-- the guy tries to pick his pocket, but Wario picks his instead, proceeding to taunt him. Then, halfway recalling his own shitty start, he gets an idea, and offers Waluigi the chance to help-a him out, cause there's this doubles tennis tournament and I want'a get the boatload of cash that comes with the trophy.
Later on, after spending all the stuff from whichever Wario Land on various things, he gets the idea to open up WarioWare as a means of getting fast cash. One thing that's of note is Wario's lack of castle-- this just further symbolizes Wario's change of mindset, how he no longer gives a fuck about whatever the hell Mario's doing, and now cares more about experience over possessions (including the experience of getting a bunch of cash with as few individual moves as possible).
Thank you for attending my Ted Talk.