Anybody help Me to buy a perfect pc.

Hi
Tell us the details of your current computer so we can help you better. You may be able to reuse components that are currently on your computer

300 to 600 dollars is a very limited budged so consider to build your own PC with some second hand components and go for 600 because 300 is simply a to limited budget.

What you need is a;
Computer case +/- 40 dollars (new)
ATX motherboard +/- 60 dollars
CPU (central processor) +/- 80 dollars
CPU cooler +/- 10 dollars
RAM (main memory) +/- 40 dollars
GPU (graphics card) +/- 150 to 200 dollars
SSD (solid hard drive) +/- 80 dollars (new)
HDD (classic hard drive) +/- 40 dollars (new)
PSU (power supply unit) +/- 80 dollars (new)
DVD drive +/- 15 dollars
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Around 565 dollars total

Look for a decent midi tower case that can fit ATX form factor motherboards.
Probably best to go for a new one because it does not cost so much and you probably gonna use it forever. Maybe something like this (https://www.amazon.com/iMicro-CA-HX310-USB3-0-Gaming-Supply/dp/B07L7FG3XF/ref=sr_1_3?dchild=1&keywords=mid+tower+case&qid=1608381306&refinements=p_36%3A2000-4000%2Cp_n_feature_six_browse-bin%3A2057506011&rnid=2057420011&s=pc&sr=1-3)

You could for example go for a second hand motherboard that uses the older DDR3 memory instead of the new DDR4 memory, that keeps the cost of the motherboard and the memory lower and you can find complete combos now for very decent prices, take for example this one. (https://www.ebay.com/itm/Motherboard-Combo-i7-4790k-32GB-RAM-Gigabyte-GA-Z97X-SLI-with-I-O-Shield/383865740769?hash=item59602e5de1:g:aVUAAOSwX1JfOtOZ). Its still a very decent chip-set and it even has a M.2 slot for fast NVMe SSD so that's very nice for fast loading of large data sets and faster file saving. You can get a new M.2 NVMe SSD for less than 80 dollars these day’s, this one would be good option (https://www.newegg.com/samsung-970-evo-500gb/p/N82E16820147690?Description=samsung%20970%20evo&cm_re=samsung_970%20evo-_-20-147-690-_-Product)

A powerful graphicscard is also a must have so maybe go for second hand Nvidia GTX 1070 or 1080 for around 150 to 200 dollars. Maybe something like this (https://www.ebay.com/itm/MSI-NVIDIA-GeForce-GTX-1070-GAMING-X-8G-8GB-GDDR5-DirectX-12-Graphics-card-w-box/264977727050?epid=26034671585&hash=item3db1e73e4a:g:0dkAAOSwZ3Ff2MLf). If you can spend more on the GPU then maybe go for RTX 2060Ti or 2070, 2080 is probably out of reach budgetwise.

Also take a decent amount of the budged to get a good PSU (power supply unit), you will keep using that throughout all your PC builds so by one that lasts. A Seasonic, be quiet or corsair 80plus 600watts PSU would be good options.

Apart from your fast M.2 NVMe SSD (operating system main disk) you would also want some large volume HDD (hard drive) preferably some 2 terabyte disk from Western Digital, Samsung or Seagate. If you can find two 1 terabyte drives for the same price then that would maybe allow you to make a mirror drive for safer storage. You can probably get away with a 50 dollar budget on those. Note, avoid 5400RPM disks those are slower then 7200 RPM disks.

Also note that second hand motherboards and CPU’s usually don't come equipped with a cooler so probably just buy a new one that matches yours. Keep in mind it should match the type of CPU socket your using so if you for example get some intel motherboard having LGA1150 socket then the cooler should come equipped with socket 1150 support bracket.

Anyways, if all of this sounds to far out then just go online for self build PC tutorials.
Its not hard, probably the hardest part is carefully installing the CPU (if not already on there) and apply some thermal past before attaching the cooler to it.

Of course you could simply buy a complete second hand PC to avoid all the researching and learning but that's just boring. Getting in the details and find the best bang for the buck is way more interesting.

For good performance at a reasonable budged at this time;

For mainboard the ASUS PRIME X570-P +/- 150 dollars
For CPU the AMD Ryzen 7 5800X, 3,8 GHz +/- 450 dollars
For CPU cooler the Cooler Master Hyper 212 Black Edition +/- 30 dollars
For RAM memory G.Skill Ripjaws 32 GB DDR4-3200 Kit +/- 130 dollars
For GPU the Nvidia RTX 3080 +/- 850 dollars
For M.2 drive the Samsung 970 EVO, 1 TB SSD +/- 130 dollars
For mass storage 2X Seagate BarraCuda 2 TB in mirror mode +/- 100 dollars
For PSU the be quiet! Pure Power 11 600W +/- 80 dollars
For case the Cooler Master MasterBox E500L +/- 40 dollars
For DVD drive ASUS DRW-24D5MT +/- 18 dollars
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Around 2000 in total

Note, I run 32GB of memory and 90% of that volume gets used on regular basis.
Actually sometimes need to keep my eye on the system monitor when more complex tasks are performed to avoid reaching the limit. With 16GB I would probably crash my system on a regular basis. I'm actually considering adding another 32GB and go for 64GB to have some more breathing room.

Anyway’s, If you look for memory you should take note of its clock speed (match or exceed it whit what the CPU can handle) and also its latency’s (CAS, tRAS, tRCD and tRP) are important, lower latency is better, 16-18-18-38 for the G.Skill Ripjaws, that's good bang for the buck.

As a CG artist its good to become a bit of a hardware enthusiast and follow up on all the new developments in the field. Knowing a thing or two about it can sharpen your judgment on when its time to upgrade and what platform you should aim for, etc. Your workstation is an important part/tool in your development and the software tools always follow new hardware improvements (like for example RTX rendering). So its nice to be able to follow those latest developments and take advantage of the new tools performance boosts.

You cannot buy the perfect pc to that price

Good luck man :p