what should be done first?
Check electricity price on your area and reserve location (e.g. your basement) to host your mining rig.
Also, what type of mining rigs should I buy, there is no problem with the capital,
Antminer S19 XP. If it's not available for you, you can use
https://www.asicminervalue.com/efficiency/sha-256 to find Bitcoin/SHA-256 ASIC with good energy efficiency.
I just really want to try, and at least before the bitcoin halving comes, I have already started this kind of thing.
If you only want to try for
short duration and absolutely have no intention to make money, consider mining Bitcoin testnet with old GPU instead. If you're interested, check
[Guide] Solo mine testnet bitcoins with bfgminer, Bitcoin Core, and a CPU/GPU.
Intend to buy the following,
--snipped general computer hardware--
What do you think about this I am planning with, is it good or can you suggest me other things?
As @Z390 said, there's almost no profitable coin which can be mined with GPU. See
https://www.whattomine.com/.