Running full node these days is a bit more demanding.
1. If you don't want to run fulll node under pruned mode, you'll need at least 700GB to store whole blockchain (and other data).
2. If your device have less than 12GB of free/unused RAM, sync process could take longer after reaching certain block height.
Then you're ready to go. There are multiple approach to achieve your goal, but the common advice is
1. Install Bitcoin Core[1].
2. Install Fulcrum[2]. It's Electrum server, which is relative light[3]
3. On different device, you can choose either Electrum or Sparrow Wallet to store your Bitcoin. But make sure it only connect to your Electrum server, to preserve your privacy.
(By the way, I don't really understand the point of buying on a DEX because the money does come from a FIAT bank account, so it's traceable because FIAT bank have your KYC.....
??)
??)The bank is less likely to know that your transaction is cryptocurrency related, unless one of you add note which mention cryptocurrency on the bank transfer. Besides, buying with fiat isn't the only option.
[1] https://apps.umbrel.com/app/bitcoin
[2] https://apps.umbrel.com/app/fulcrum
[3] https://www.sparrowwallet.com/docs/server-performance.html