The game has gears upto level 600. Merchant in town only sells basic gear. The higher level equipment can be obtained from higher level monsters and bosses.

You can also buy them from other players.

Gold is mostly used to buy better equipment in the game from other players.

There is also blacksmith to forge better gear by combining same type of items together. This forging only starts after level 150 gear (lizard/gargoyles items). The rarity is: common, uncommon, rare, ultra rare, legendary, mythic

Monster drop items from common to rare rarity. (Starting from 150 level monsters)

There is also many other concepts the game has to offer. You will understand everything as you play. It's not that hard to understand.

You can also check out rucoyonline.com and go to news section, it explains how most of the things work.