There are around 60 cards in Magic in blue, red, and white that have convoke, giving you a healthy selection of cards to pick from to fill out your deck
Cards such as LOB Blue Eyes White Dragon, Red Eyes Black Dragon, Dark Magician and the Exodia pieces
So, if your opponent is at 20 life, you need nine spells, followed by a Tendrils to make 20 damage
Card border and frame details: A simple Silver or Goldenrod outline around the character mimics the look of a real trading card without needing extra detail
It is fairly common for your opponent to have a sizable battlefield presence with large blockers, and you just attack with all your disposable creatures and then use Conflagrate to finish the blockers off after damage
Making sure to include some lands that you can tap for any color will give you more chances and more options