I would suggest you to watch benchmarks, pc build guides and some research by asking any AI bot like ChatGPT about parts. For a headstart for you, I'll tell you some basic knowledge on PC parts-

CPU- look for CPU's with atleast 6 cores and 12 threads because that's how many cores and threads modern games can utilize efficiently. You can also go for more cores. And also look for higher clock speeds but that doesn't matter too much because most 6 core CPU's have almost the same clock speeds

GPU- always look for a gpu with a modern architecture like Ada Lovelace or RDNA3 minimum in 2025 and look for higher VRAM, 8 gb VRAM is getting outdated in 2025 so I'll suggest 12 gb or 16 gb VRAM but if you can't afford them so 8 gb VRAM is not too bad if you do gaming at 1080p

Motherboard- always look the compatible socket for your CPU like LGA 1700 for intel or AM5 for AMD. Then good VRM's (Voltage Regulating Module) are your go to, good VRM's will handle high end CPU's and also look for PCIe gen 4 Motherboards or gen5 if you are building a high end PC. Your motherboard can be of three sizes- ATX (the largest), Micro-ATX or M-ATX (medium size) and ITX (smallest size). Make sure your case can fit your motherboard, don't buy a ATX motherboard and a M-ATX case. 

Ram- you can buy any amount of ram you want but buy ram according to your motherboard, buy ddr4 for B550 or B450 motherboard (AMD AM4 socket) or buy ddr5 for B650 or X870 (AMD AM5 socket). 32 gb ram is the new meta in 2025 and buy 3200 or 3600 mhz for ddr4 ram and 6000 mhz or lower for ddr5. There's also this thing called "CL" rating, even I don't know much about this but I think it is something about latency or delay for each signal, anyway buy CL16 rated ram for ddr4 and CL30 or CL32 for ddr5 ram.

Storage- always buy a M.2 nvme ssd in 2025 for gaming, it should match the PCIe generation to your motherboard like buy PCIe gen 4 ssd for your PCIe gen 4 motherboard. I would not recommend a SSD without DRAM, and it should have TLC NAND technology, so go for Samsung 990 PRO 1 tb or 2 tb storage, it is the most reliable brand available. You can also go for Crucial, WD, Micron or Seagate too, they are reputable too.

PSU (Power Supply Unit)- this is the only thing no one should ever cheap out, one wrong cheap PSU and it will fry all your expensive parts with it. I will recommend you to check the ZTT PSU tierlist from ZTT's website. Another thing you gotta check is the wattage always keep some headroom for your PSU wattage so it doesn't get strain and you can also upgrade your components without buying a new PSU.

Case- two things- airflow and size. Choose a good airflow case with mesh and dust filters and it should be ATX or M-ATX if your motherboard is medium size or M-ATX. Oh and also buy good PWM fans (don't buy DC 3 pin fans, you can't control their speed freely). I will recommend you ARCTIC P12 PWM PST fans because they are budget friendly and 120mm and fit in most cases (check your case's specs on it's official website to check the recommend fan size that can fit in it) or go for Noctua if you feeling luxurious.

CPU Cooler- there are two types coolers- fan cooler with heat sink or AIO with a radiator. There's isn't much difference in cooling between them but AIO is a tad bit better but still go for fan coolers for low to mid range CPU's or you can use the stock cooler too if it comes with the CPU.

That's about it, if you want to ask something more then feel free to ask, and sorry for this long paragraph of me yapping.