Until now to obtain btc I used localbitcoins to buy through WU, but I think it's way too expensive.
Do you suggest using exchange websites like kraken that require you to submit legal documents in order to be able to purchase with usd? I'm hesitant for security, although I know that once I have the bitcoin I can easily tumble it somewhere.
Let me know on ways you prefer to purchase bitcoin.
Kraken's very buggy but you can use whatever exchange to purchase and store the coins on your local machine with electrum wallet. And obviously send it through tumblers at each transfer. You'll be pretty ok like this. I believe that people have had their exchange accounts shut down when transferring from an exchange directly to a darknet market.