What I did successfully for some years to support myself almost entirely on magic the gathering. Forgive my swapping between "I" and "You" a bit here.... It's advice but at the same time my old story, so I bounce back n forth on a whim. Enjoy!
Preparations
Carried this bad boy around for a long while...
source amazon
While writing this article I came across this bad boy which just got added to my wish list.
Every set release, load up on sub $1/ cards, aiming for about 20 if each. Immediately load up 4 in the trade binder (I typically would alternative between 4in a single slot and 1each, depending on a variety of reasons to choose from, art, subtypes, synergy with the other 4 or 1 of on that page, etc. Put some time into presentation. Also, 100% recommend vintage or other unique binder options, just make sure they won't wreck your cards in any way, adding spacers or other padding helps with this, modify your binders, people love that type of stuff, it's memorable. This is your "sub$1 binder".
Just don't be this guy:
source: Amazon
source: Amazon
trading
Load up your briefcase suitcase with some spare cards (and your value binder if you dare), and hand carry your sub$1 binder, this is what you plop down on every table you see someone you haven't talked to that day. You don't even have to offer trades, you could lead with ask if they want to look at your cards. Do this every chance you get when going into a shop for any reason. Trying to hit at least 3 nights a week at a variety of shops.
I try to toss the values out of the window during the "negotiating" stage. Let them know to take out anything they might think is cool or they are interested in and would love to trade. Don't pressure or suggest initial offers, back seat and accept what comes your way. When pulling cards, I'm always aiming to trade for cards that see play (micro and macro here, local play is often different than large events and both hold that value differently) or think there is a good chance it could hit other formats as a staple or spikable. Trade for $3-10 cards, occasionally toss a $10+ in the 'trading for' pile.
Not the typical backpack dealer,... Just a bro trading cards.
People that know you and what you are up to.... Still humor the grind. Try not to take advantage of the guys who are hyper casual and insist on 1for1 trades, let them know the value is definitely in your favor and at least insist on 3-5+ of yours for their $20/ you'd be surprised how many people will still insist on 1for1, just do it, because if you don't, the next guy will, this type of trader doesn't care about financial value, they just want what they want, and happy to help someone out.
Eventually they will even seek you out as the "honest with their intentions" trader out there. Building a reputation and trust, and they know you will have those obscure cards noone else has.. all those guys loaded up with $5+ cards only. Variety is the spice of life they like, not the same ol cards everyone else is playing. Also, gives you that bonus lottery of having copies of cards that go from $0.35 to $20 because insert major tournament here spiked them. Don't cash out too much to buy lists... You are already leaving the house to go play and trade, drop some eBay or tcgplayer sells in the mail on the way down to wherever. Facebook groups and marketplace is interesting here as well.. but that's a whole other random off-topic comment noone asked for.
Stay real my fellow humans, 🤘🤘🤘✌️