@BellyacheSimmer This doesn't at all qualify as a late reply—I've seen people come back months later. And school is definitely more important, as fun as shopping for a new computer might be.
A couple of details are useful to keep in mind when you have a bit of wiggle room in your budget. Memory and hard drives are extremely easy to install, either yourself or at a store. RAM clicks into a slot, and you're done; a hard drive needs to be slid into a slot and connected to the power supply and motherboard by cables, nothing more. (This is what it looks like, if you're curious.)
Graphics cards can be swapped out as well, although it's more complicated: the physical installation is a bit trickier, plus you'd need to make sure your power supply and motherboard supported the new card. A new processor usually means a new motherboard, which means rebuilding your computer from scratch. So if you're thinking about future upgrades, keep in mind what you'd need to do to swap out a given component.
Given what you want, I saw a few good options that were significanly cheaper than everything else. This one is the lowest I'd go though. Its graphics card, and AMD Radeon RX 580, should handle Sims 3 (all packs included) on ultra settings, even in QHD, but it's not really futureproofed for newer games. On the other hand, it's $620 on Best Buy and Amazon.
https://www.bestbuy.com/site/cyberpowerpc-gaming-desktop-amd-ryzen-5-1600-8gb-memory-amd-radeon-rx-580-480gb-solid-state-drive-black/6371594.p?skuId=6371594
https://www.amazon.com/CYBERPOWERPC-Master-Gaming-3-2GHz-GMA8980CPG/dp/B07W62CJCQ/
The next faster graphics card that's widely available is the Nvidia 1660. The Super and ti versions are about 5% and 6% faster than the standard version, but even the standard one is overkill for Sims 3 (and 25% faster than the RX 580). There are many different models with a 1660 in the $800 range, but this one, at $750, clearly has the best hardware. It comes with 16 GB RAM and an AMD Ryzen 3600, a processor that should be strong enough to handle whatever your plans are for at least five years, if not more. The motherboard and power supply should also support a faster GPU in the future. I believe the Amazon model is exactly the same as the one on Cyberpower's site, in case you don't want to order from Cyberpower.
https://www.cyberpowerpc.com/system/Gaming-Instant-Ship-GM-9910
https://www.amazon.com/CyberpowerPC-Master-Gaming-GeForce-GMA1400A/dp/B07X31NT47/
These two computers only have a single 500 GB solid state drive. You definitely want an SSD for Sims 3, not to mention Windows, and 500 GB should be enough for TS3 plus saves, mods, and custom content; your other "minor games"; and whatever other random apps you'd like to install. And you could add more storage later, if you wanted. But if you'd prefer not to need to, there are other options with a smaller SSD and a larger HDD. The thing is, with a 256 GB SSD, you'd need to manage your storage carefully to make sure Windows kept enough room to maneuver.
Having said that, here are more options. This one is also $750, and it has only 8 GB RAM, plus a processor that's significantly weaker, but still more than good enough for TS3:
https://www.amazon.com/CYBERPOWERPC-Xtreme-i5-9400F-GeForce-GXiVR8060A8/dp/B07VGJDKZ4/
This one is $800 and has 16 GB RAM, even more storage, and a processor that's better than the 9400F above but still significantly behind the Ryzen 5 3600:
https://www.bestbuy.com/site/cyberpowerpc-gamer-master-gaming-desktop-amd-ryzen-5-2600-16gb-memory-nvidia-geforce-gtx-1660-super-2tb-hdd-240gb-ssd-black/6401035.p?skuId=6401035
This one ($750) has the Ryzen 5 3600, 8 GB RAM, and the RX 580 GPU from the first link:
https://www.bestbuy.com/site/cyberpowerpc-gaming-desktop-amd-ryzen-5-3600-8gb-memory-amd-radeon-rx-580-2tb-hdd-240gb-ssd-black/6362427.p?skuId=6362427
I could spam you with lots more links, but there was nothing else I saw that was better than the ones above for a similar price.
And please feel free to ask more questions. Come back whenever you have time, and I'll be around sooner or later.