>>2205
>Where would I buy it
There's Bisq, a distributed marketplace where you can put dollars in by various means, buy BTC and then buy other coins with BTC. There's a ton of other marketplaces. If you're in the right country, you can even buy vouchers in local shops for some marketplaces.
>What payment methods would I have to use?
Varies by marketplace, heavily so. You can practically find a marketplace for any payment method.
>Would the taxman notice this?
With most mainstream places, yes. The problem however lies less in how you acquire the initial coins, but how they develop until you sell them. There's coin washing services that are meant to confuse traces of what actually happened afterwards, but if your marketplace has anonymous coins like Monero (XMR) and allows payout to a wallet of that coin (each crypto has their own wallet system), then you can use an anonymous coin to buy another coin on an exchange that doesn't ask for confirmed ID and you can have anonymous investments the taxman cannot find.
Say, you put dollars into Bisq and buy BTC. This requires a real identity, unless you can find someone willing to trade in person for cash. Then, you use those BTC to buy XMR (ticker name of monero) on a monero wallet. Then you go to a different exchange, send your monero to that wallet and buy another currency there (or stick with monero).
You can then either outright pay with crypto for stuff (some sites allow it, especially darknet, and there's some physical stores that allow it too), sell it to people in-person to get fiat currency, buy amazon giftcards with crypto (some marketplaces allow this) and just shop there, or buy giftcards and sell them on ebay, or buy stuff or giftcards with crypto; buy goods with them; and then sell the goods on ebay. The fiat currency part really is no different from basic money laundering.