Search your library for a card that shares a color with a legendary creature you control, reveal it, put it into your hand, then shuffle
They also have dedicated land support with Haven of the Spirit Dragon, Crucible of the Spirit Dragon, and Temple of the Dragon Queen, making it easy to support a 5-color dragon deck
Building a deck is all about having an angle and knowing which cards work the best together, something that even non-playing collectors can relate to
If youre looking for a simple, inexpensive way to get into Commander, Id personally recommend looking at other options like previous precons or the upcoming Commander Starter Decks
You can sacrifice lands and pay a small amount of mana for various effects, like drawing a card or giving it unblockable