First,
you need to understand that stickers (including gold stickers) are used
to complete sets and advance game progress. Currently, there's no clear
method for obtaining gold stickers. However, players can increase their
chances of obtaining stickers by participating in game events and
trading with friends. The introduction of "gold locks" means players can
only obtain stickers through sticker packs, not through trading.

You can quickly buy Monopoly Go: Bon Appétit gold album, Bark the Halls
4Stars-S16-7, and Snow Day! 4Stars-S18-5 at low prices on IGGM.
Stickers (including gold stickers) can be earned by participating in
daily activities. Stickers can also be earned by completing attribute
sets and opening community chests.
While a "gold lock" mechanic prevents players from obtaining gold
stickers, they can trade them with friends to obtain other valuable
stickers.
Recently, the official announcement of a limited-time event has been
made. This event will feature two new gold stickers. If desired, you can
buy Monopoly GO stickers on IGGM
While these stickers are limited to personal collections, they are still
highly sought after by many players because they allow you to further
expand your sticker trading collection and potentially complete
higher-level albums for lucrative rewards. This event is only a week
after the last one, but it's no surprise that it's releasing more
content and gold stickers.
This event features two gold stickers: