You can buy at Kraken, Coinbase and Crypto.com. Outside the US add Binance.
Add xt.com and binance.us to trade. xt has a lot of tokens that others don't have.
Most of my trades are done using a Phantom wallet and Jup.ag since I love everything Solana. Jup is a DEX but you still can place limit...
You can buy most things with bitcoin. People live off it. They buy gift cards including Amazon.
Bitpay is a prepaid credit card. It's no longer available in the US but you just load crypto on the card.
That article says it all. Institutions are buying up more than is being created and the amount created is getting cut in half. Most retail investors haven't even jumped in yet. Monster run ahead of us.