RPGMemes

Not the richest fastest but probably nice and discreet: electronics repair shop using mending.

Lawful Good:

Foresight to convince the smart, powerful people that they're making bad decisions, influence them to make better decisions for the world, only use it for enough personal gain to sustain a decent living.

Neutral Good:

Mass Suggestion Convince the dumb powerful people I'm a divine being and they better do as I say, use this power to force positive change amongst the easiest to control masses. Collection plates at churches now go to me.

Chaotic Good:

Gate, Use teleportation to extort billionaires by witnessing their depravity and threatening them with exposure, also portal tech. become Rick Sanchez. Rob swiss banks for fun and profit.

Lawful Evil:

Meteor Swarm: Hold cities hostage for ransom.

Chaotic Evil:

True Polymorph: I'm going to start turning politicians into lizards. For cash I'll turn random shit into itself but but made out of a different material and auction if off, passing myself off as a great artist of incredible talent.

Edit because I forgot about the money half way through.

To maximise staying under the radar, probably fabricate. You'd not be amazingly rich, but you could establish a decent living with a lot of free time. If you want to be amazingly rich and you squint hard enough at fabricate and what tool proficiency count mean in the modern world you can probably make some bank with a bit of study of chemistry or engineering. Being able to magically create complex drugs or something is going to draw attention though.

Fireball

Step 1. Cast foresight
Step 2. Go to Vegas
Step 3. Profit

Welcome to GoodBerry, Home of the GoodBerry. can I take your order?

Mage hand and offer ghost handjobs for $1000 per person per handjob

Prestidigitation, and a residency in Las Vegas. David Copperfield was able to buy a private island, imagine what I could do with real magic!

Prestidigidrycleaners.

Seriously though, it's Locate Animals Or Plants and going truffle-hunting.

The chaotic-neutral answer is Heal, and ending blindness, deafness, and other diseases... sometimes. One in three. You do some faith-healer hokum, make a ton of false promises, and ensure that people get whatever medical care they can. Then you genuinely perform miracles just often enough to leave people wondering. Sometimes treatment works! You never know! Hell, a few people you don't heal will swear you did.

Druidcraft can probably abuse the hell out of saffron prices.

Disintegration is a six-second lockpick for any door, gate, ATM, or other obstacle to simple burglary.

Dimension Door for bank robbery. Piss easy: pop in, grab as much as you can carry, pop out.

Demiplane allows for proper heists: create door near valuable stuff, put stuff in big empty temporary room, recast spell later to create door in hideout. Anyone mildly clever would figure out how to be allowed near valuable stuff without just teleporting to it. Anyone properly clever would figure out how to have other people move valuable stuff into that arbitrary room. At least you could decorate beforehand to look more legitimate.

The evil answer, for demiplane, is to create traps where you let people die. Anyone inside when the duration ends will be a body to loot when you reconnect in a month.

Geas allows a complicated scam: you sell an ad campaign to some advertising firm, by convincing a few schmucks to act in accordance with your advertisement. None of those people's money goes to you. Your income comes from the bastard corporation that thinks you've unlocked another billion-dollar shadow economy, for their... I dunno, rat-themed child casino and pizzeria? Whatever they're selling. Just make up some basic Got Milk nonsense and then engage in superliminal advertising the next day. Like that Family Guy bit: Smoke.

Bonus points for the ad thing if you work in Hideous Laughter. That shit's first-level.

"Magnificent Mansion ghostly servant brothel" is probably not a good way to stay on the down-low.

Not super creative, but distort value would work pretty well. People would think you're just a really good salesperson.

Teleport from children’s hospital to children’s hospital casting heal.

DM says no

Fine raise the dead.

Phantasmal Killer, assassin for hire.

Polymorph, make an only fans.

Move Earth, get a job in construction.

Animate Dead, free labor

Magic Missile never misses

Summon monster (fire elemental) free clean power generation

I could go on all day. Having wizard spells would literally make you stupidly rich.

Suggestion. And then go to Wall Street :)

True Polymorph is the easiest if we just wanna accrue wealth quickly

Buy some live feeder mice (a small animal that doesn't involve killing someone's pet) and transform them into jewelry. True Polymorph has none of the restrictions of Fabricate, so we can create fine jewelry without skill. Turn a mouse into a gold ring or necklace, with a large gemstone embedded into it. Sell it at a pawn shop. Repeat, use different pawn shops, and use Dominate Person with Modify Memory afterwards if theres some law about needing an ID. The dominated person can use theirs, and then you remove the interaction from their memories.

Sell fine jewelry made from mice all you want. Use that cash to buy cows or other massive animals, turn them into gold. We don't have to worry about how to pass the gold off though, the goal was to accumulate wealth. Use Fabricate to make the cow-gold into rough coins, build a secret dragon's den.

Of course, if we're willing to be a little less subtle, True Polymorph is also great for doing some light faith healing, restoring blindness due to injury by transforming them into another person that's basically identical, or we could make people look like their ideal selves. Not in the bounds of the question though.

Eldritch blast + spell sniper for no particular reason

Fireba- Oh wait, without drawing attention? Invisibility and Dimension Door to steal riches.

You could get some great use out of fabricate and proficiency in something related to computer architecture.

Legend Lore could equally grant you valuable knowledge to sell, and similarly half the divination spells could make you a very successful gambler.

1. Learn charm

2. Use it to get hired as the pastor of a megachurch

3. Use it on the congregation

Foresight and gambling

Use Augury to slightly improve my odds in online poker. My winnings are legal and legitimate, I don't have to leave the house so no one can tell I'm doing magic, and there's nothing to notice other than I'm unusually good at the game.

EDIT: On second thought, online sports betting is a thing now. I'm changing my answer to that.

I convince people to buy my junk using Charm for exorbitant prices.

Mending, open a phone repair business. People would just think I’m really good at my job!

Also: Borrowed Knowledge + Fabricate

Astral Projection head to America set up an evangelic church

At a high enough level, I’d use creation on either gold or diamond. Might be hard to sell a 5x5 block if either but you’d make good money if you could. Or just become a human 3D printer and sell off the things you make.

Boring

Invisibility,

swipe money from anywhere that old large amount of cash

Or use it to watch people enter passwords?

If there is a spell capable of breaking down things into its basic raw elements, that would be it.

Garbage is abundant, as well as junk.

Imagine deconstructing anything back to its basic elements and then sell it. A gigantic pile of mixed junk instantly deconstructed and turned into ingots of pure metals, carbon, and other elements.