If you want to skip the "tickets" middleman, major retailers allow you to buy singles directly with a credit card or PayPal on their websites.
: You can build a deck on their site and pay with cash; they will then deliver the cards to you via a bot trade in-game. buy mtgo singles
Buy Event Tickets from the official ($1.00 each) or authorized third-party sites. Search for a bot (e.g., "GoatBots") in the Trade tab. If you want to skip the "tickets" middleman,