For me, Gmail is FANTASTIC about quarantining spam. My spam folder gets 50-60 a day and I never see them. It auto-deletes them after a few days. I do get marketing emails from time to time, but once I unsubscribe, they stop.
The "unsubscribe" button in Gmail isn't foolproof. That button tries to do the legwork for you, but it doesn't always work. If you really want to unsubscribe, follow the link in the bottom of the email and do it yourself on the unsubscribe website that pops up. As I understand it, if you unsub from a company's email, and they send you another one (in the same category) it is most illegal. When I say in the same category, I mean to say - if your bank sends you an email that says "apply now for a refinance and get a free toaster!" and you unsub from that, they are still allowed to send you an email that says "we noticed you haven't paid your mortgage, Rico, please give us a call."
If the subject of the email is "Don't miss our 20% off membership deal" from Costco, that's just marketing. Click the link to unsubscribe, and move on. They're advertising to try and get you to buy their product. Do your due diligence, though, and check the sending email address. If it says marketing@costco.com, you're likely safe. If it says fakeymcfakerson@india.suckerborneveryminute.com, don't click it.
If it says "eN-Laarge y.o.u.r p-en-i$", that's likely a malicious email setup by someone using a known network of botnets (grandma's Win7 laptop that she forgot to turn off in 2001) and you should report it as spam, delete it, and do NOT click anything in the email.
The malicious emails don't find RevRico@Gmail.com and decide to spam you. A bot is somewhere churning out lists of generated emails that basically make up every possible email address on the planet. It starts with 1@1.com and keeps going. That's how spam phone calls work as well, BTW. I'm in 717 area code. They don't have my phone number, but a computer generates a list of every possible combination of numerals for the last 7 digits and starts calling. That's why if you pick up the phone, no one is there for a second or two. They're like 'oh crap, someone picked up. That's an actual number." If you click unsubscribe or interact with anything in the email, they now know they have an actual email address which can then be targeted... hacks, marketing, malware, etc.