In Assassin's Creed Origins, you need money (Drachmas) to upgrade your weapons and to buy better equipment / gear.
Bellow are some of the easiest and best ways to farm quick money in AC: Origins. Here, you’ll need some patience and time but in the end it pays off.
Side Quests: Side Quests in AC: Origins are one of the best ways for you to earn some extra money and most of them don't take long to complete. For example, if you complete the side quest "The Last Bodyguard" in Alexandria, you'll quickly earn 500 or more drachmas.
Loot: Unlock your Auto loot ability so that you can automatically loot when you kill an opponent. You can also use Senu or Animus scan abilities to scan all areas. In this way you’ll find a few drachmas hidden in many vessels. In addition, you can also sale unwanted items / loot and make quick money. If you sell 100 unwanted items at once, you will also get “Reduce, Reuse, Recycle” achievement.
Chariot Races: Wining a Chariot Race / tournament will bring you 100 or more Drachmas. You have to chase the Chariots through the Hippodrome for a while, but once you get the hang of it, you can earn more cash here. If you also win horses, you can exchange them for cash.
Hunting: Bayek can also equip a hunting bow. Scan an area for game with Senu and go for the trail. Especially in low-level areas, you can quickly and easily get rare and legendary skins and leather that you (if you don’t use them in your equipment) can sell them to the merchant for a large sums of money.
Papyrus Puzzles: Yes, they can be tricky but if you solve one of the puzzles then you can earn 300 drachmas.
Helix Credits: If you're willing to invest some of your real money to make Bayek richer, you can invest in packs and get into drachmas through helix credits. Actually, this is not necessary, because the game offers enough opportunities to get money for Bayek, without spending your own money.