How do bonus tiles and booty tokens work?
Having now looked over two different English translations, I'm better able to figure out some of the ambiguous wording.

Bonus Tiles have the same coloring system as gods: gold backgrounds mean "play immediately, then discard," and blue backgrounds mean "keep."

All bonus tiles are revealed immediately after the first Prepare-Civilization phase, and all gold tiles are immediately executed and discarded. (If you got the God bonus tile, and it's one of those gods that give you a bonus every turn, you don't get that bonus this turn; using that tile happens after the phase in civilization-preparation where you'd get the bonus in the first turn.)

The "Movement" Bonus Tile is kept permanently, and gives +1 Move on every movement action. (You're not required to use it each Movement action, though.) This can add up to a quite decent bonus over the course of the game.

This means that the single-most-useless tile is the one that upgrades a sacrifice tile, because you're required to use it immediately, and you can only use it to buy a Level 1 tile. This makes it worth one-gold-plus-the-buy-action-to-acquire-it, which isn't particularly useful because you're allowed to do many things during a normal buy action.