Upgrading a pre built will have limitations.
Games will be limited either by the cpu or the graphics card.
A stronger processor is likely reasonable.
What are the cpu upgrades that acer allows on that pc?
CPU-Z will identify the motherboard.
Graphics upgrades are also possible if the power supply is strong enough.
Unfortunately pc builders only include sufficient power to run the initially ordered components.
Look to see if your psu has a 6 or 6+2 pcie aux power lead that stronger graphics cards will require.
Do not buy a cheap replacement psu.
Plan on $100+ for a quality unit that will last
I see you have a GTX1050 mini. Is your case restricting the length of a prospective graphics card upgrade?
As a simple quick test,
Run YOUR games, but lower your resolution and eye candy.
This makes the graphics card loaf a bit.
If your FPS increases, it indicates that your cpu is strong enough to drive a better graphics configuration.
If your FPS stays the same, you are likely more cpu limited.
Stronger components will also want to be well ventilated.
It looks like your case is not a great one for air intake.
One upgrade that is easy and very satisfying would be to replace the HDD with a ssd now. A 1tb samsung 860 EVO is about $100.
2tb is twice that.
Everything will be quicker but not for gaming.
A ssd upgrade can be carried forward to a new build later.
8gb is not enough, but simply adding 8gb may not work, ram must be matched to insure proper operation,
All this is suggesting that a new build is in order, but, I do not think you can do it all on your budget.
I might suggest a i3-10100 processor, a 2 x 8gb DDR4 ram kit and a lga1200 motherboard that fits your case could be had for $250 or so. A GTX1650 class card would be in the $150-$200 range.
Such a card is about the strongest that will run without aux power.