system
A chat on subreddit /r/pcmasterrace
human
Game wise, you could play nothing. Modern at least. You might get away with League of Legends, and Minecraft Bedrock. Minecraft Java, any other game, no chance.

As for what you should upgrade, definitely go GPU first. Here are a handful of GPUs that I found that’ll fit:

1.) AMD Radeon RX 6400 Low Profile Gaming Graphics Card 

(2.) MSI GTX 1050 TI 4GT Low Profile  Graphic Cards

(3.) Gigabyte Geforce GTX 1050 Ti OC Low Profile 4GB GDDR5 128 Bit PCI-E Graphic Card (GV-N105TOC-4GL) 

(4.) GIGABYTE GeForce GTX 1650 D6 OC Low Profile, Low Profile GV-N1656OC-4GL Video Card

(5.) Gigabyte GeForce GTX 1650 D5 Low Profile 

(6.) MSI Gaming GeForce GTX 1650 4GB GDRR5 Low Profile Graphics Card (GTX 1650 4GT LP OC) 

I also found a few gt 1030 cards, but the way games are going right now, they’ll be useless in a few months. The 1050ti is decently old and might struggle a bit at 1440p, but if your budget is limited, that’s the best option

Then you’ve gotta choose between the 6400 and 1650. The 1650 is slightly better even though it loses to the 6400 in raw teraflops, mainly because of its faster memory clock, and more texture mapping and shading units. It does however cost ~$80 more. The choice is yours

The next upgrade I’d go for is the RAM. Most kits should work as long as they fit in the case. Make sure whatever you buy is ddr4 and don’t bother with RGB, because you’ll never see it anyway, it’s just more power consumption on the tiny PSU. Here are a few kits I’ve picked:

(1.) Crucial 32GB Kit (16GB x 2) DDR4 3200 MT/s (PC4-25600) 

(2.) Crucial 64GB Kit (32GBx2) DDR4 3200 MT/s

(3.) Crucial 8GB DDR4 3200 MT/s (PC4-25600)

(4.) Crucial 16GB Kit (8GB x 2) DDR4 3200 MT/s (PC4-25600)

You probably don’t need or want 64GB, but the option’s there. You’ll probably want to replace the default RAM. Because it’s a bit slower than the CPU’s potential.

The next thing is the storage. I’m kind of unsure what it is because it says HDD and solid state drive, but regardless, you’ll run out 256GB quite quickly. Here’s a few NVMe’s:

(1.) Crucial P3 Plus 4TB PCIe M.2 2280 SSD 

(2.) Crucial P3 Plus 2TB PCIe M.2 2280 SSD 

(3.) Samsung (MZ-V7E1T0BW) 970 EVO SSD 1TB M.2 NVMe 

(4.) Samsung 970 EVO Plus SSD 500GB 

(5.) Samsung (MZ-V7E500BW) 970 EVO SSD 500GB - M.2 NVMe 

(6.) Crucial P1 500GB 3D NAND NVMe PCIe M.2 SSD - CT500P1SSD8 

4TB might be overkill, but still the option is there. I’d recommend at least 1TB maybe 2 if you have a lot of data.

At this point though your PSU probably won’t be enough to power everything. 300W isn’t enough for all of this. Consider seeing what could fit in the power constraints online using a PSU calculator like newegg’s.

If you do want all that power, try and find a 400, preferably 500w PSU online. From what I’ve found, the PSU in your PC is a unique form factor that puts all 300w over one power rail. You might be able to hack an SFX power supply to fit and modify the rails a little, but it would be a long endeavour.

Anyway, I’ve given you my thoughts, now it’s up to you. Good luck!

EDIT: I had to remove the links because of Rule 5, sorry but you’ll have to find the products yourself, again, good luck!
gpt
Tha k you so much for the super in depth response, I’m looking into the 1050 ti now