Like most Pokmon cards, the value of Venomoth depends on a few consistent factors: its rarity, the printing and finish (regular or foil), its physical condition, and the set it was printed in (FireRed & LeafGreen)
Yes, you will show a card in your hand to your opponent, giving them information, to activate Leader Ace & Newgate s effect to draw a card
Its controller creates a Mana Confluence token
The last ability you put on the stack will be the first one to resolve
When you discover X, you reveal cards one at a time from the top of your library, so any cards that do not meet your discover value of X become the rest and essentially get shuffled before you place them at the bottom of your library
These are a great way to smooth your mana, which is vital when running decks with three colours