1 - When there are gold left on the oasis, when a player get there, he must choose take the gold or draw the 2 cards? Or he take the gold and draw two card either?
2 - If a player looses all his equipament by turning into a toad, when other player get there, he can take everything or he must left behind some cards when the house says "draw 1 card"?
1. From Rulebook, page 9, gold, Objects and Followers are usually taken at the same time:
After any Enemies in the space are killed (see “Resolving Battles vs. Creatures” on page 10) or evaded (see “Evading” on page 14), any Stranger or Place there must be visited and any gold, Objects, and Followers may be taken.
So, if there are no cards and only gold on the Oasis, when you encounter the space you must draw 2 cards and may take any gold on the space only if you defeat or evade all Enemies, and encounter any Strangers there (they have Encounter Number 4). Just treat the gold as it were a Bag of Gold with Encounter Number 5.
2. Characters landing on a Draw 1 card space with a pile of cards/gold already there can take what they want, but must respect carrying limits and other restrictions (e.g. Alignment). They don't have to draw 1 card since there is already more than 1 faceup card on the space.