If you need/want to use Bitcoin: Coinjoin (specifically Samourai Wallet: whirlpool + run your own dojo + spending tools)

If privacy is the priority, maximalism be damned: Monero

Zcash sender privacy *tech* is better than Monero. The implementaion of it on Zcash itself...not so much: https://moneroinfodump.neocities.org/#ZcashBlackpill