Could someone explain what are some best practices for maximum privacy?
Don't use your real address but instead use Amazon lockers for delivery.
If you were to want to use it on Amazon, what would be right steps?
I think Bitreffil has dedicated Amazon cards, and they accept Bitcoin and shitcoins, so you could easily use Lightning Network or some other coin to improve privacy (swap from BTC before purchase).
There is almost zero chance LN Bitcoin will get flagged by anyone as tainted, at least I never heard something like that.
And if you mix your coins and end up with tainted coins, or someone that paid you had tainted coins whether they knew or not, you will be the one that gets doxed while using said tainted coins and you don't want that.
Forget about idea of tainted coins, and don't purchase expensive items on Amazon.
If you are so concerned and privacy and tainted bs, than just purchase things with cash.