*Buy all at once, as BTC is arguably at its lowest rate.
*Buy at intervals because of any possible variable.
You can combine those two by buying now for 50% of your budget (because BTC is super oversold right now) and do DCA for the rest 50%.
However, in my last post I expressed my disappointment with centralized exchanges, my unwillingness to continue using them and thankfully I got suggestions mainly endorsing Bisq, of which I've taken time to look into Bisq and other decentralized exchanges and observable is the absence of a support team unlike their centralized counterpart. That be the case, what are:
1. The recurring mistakes that could lead to loss of funds?
2. How can these mistakes be avoided. Since it seems like the only remedy.
If you have zero experience just stick with CEX. BUY and withdraw to cold wallet. Especially if you have fiats now, because there is no efficient, cheap, fast, decentralized fiat/crypto getaway.
If you have stablecoins you can try buying btcb on pancakeswap and than use bep20 to btc bridge.