If you are in Brazil then AM4 is your best option. The best value for money here is usually a Ryzen 5 5500 CPU, a B450 motherboard, DDR4 3200MHz Ram, a 500W PSU (look for the Nidus 550W or 650W they are very reliable and are always on sale) and a Radeon RX6600. That's already a massive upgrade from your Celeron. It can do modern games at 1080p and everything emulation wise except maybe the most demanding PS3 tittles.
What would you say that build would cost, all in, assuming no carry-over parts (like a monitor or Windows installation)? I see prebuilds for about R$4650 on amazon with that spec, though I really have no sense for pricing in Brazil.
For the sake of following the exercise, I did a skim about Amazon for MiniPC's at or under the R$5000 mark. These are the standouts, tell me if they're terrible buys:
KAMRUI Mini PC AM21
R$3.579,45
AMD Ryzen 7 8745HS (8C/16T, até 4,9GHz), 12GB DDR5 5600MHz RAM, 256GB M.2 2280 PCIe 4.0 SSD (Presuming a Radeon 780M)
Seems suspiciously cheap, given that vastly inferior CPU packages land in roughly the same price range. This seems a lopsided build that weighs heavily towards CPU performance (and integrated GPU performance) while skimping very heavily on RAM and SSD. I'm actually concerned that this is a incorrectly labelled product, given that the AM21 tends to be a 32GB/1TB model.
MOREFINE Mini PC M700
R$4.183,76
AMD Ryzen 7 7735U (8C/16T, até 4,75 Ghz), 16GB DDR5 512GB NVMe SSD (Presuming a Radeon 680M)
This probably ships with only a single stick of RAM, which would cap your performance somewhat. I'm not terribly excited by it other than the fact of it's price -- just about R$4200.
Beelink Mini PC SER5 MAX
R$4.986,90
AMD Ryzen 7 7735HS (8C/16T, até 4,75 Ghz), 24 GB LPDDR5 RAM 500 GB NVME SSD (Presuming a Radeon 680M)
I basically own two of these, but within a different chassis. They're fine, nothing stellar, fairly okay. You're guaranteed to get dual-channel performance since they tend to run those LPDDR clusters sensibly. But, a bit more expensive.,
As far as CPU compute is concerned, all of those MiniPC's ought to meet or exceed Ryzen 5 5500 performance. They'll all lag far behind an RX6600 on graphical performance, but should rival or beat a Steamdeck, which is something that we can also get for around that R$4500 pricepoint.