Two-player gem game (emeralds and pearls)

Two players play a game. They start with a pile of emeralds and a pile of pearls. On a turn, a player can take: any number of emeralds (at least one); any number of pearls (at least one); or an equal number of emeralds and pearls (at least one of each). A player must take at least one gem on each turn. The player who takes the last gem wins.

Example: starting with 5 emeralds and 10 pearls, Player 1 takes 2 emeralds; opponent takes 7 pearls; Player 1 takes 3 emeralds and 3 pearls to win.

You may choose the starting number of emeralds and pearls, and whether you go first or second.

1. Find all starting configurations (including who goes first) with a total of 8 gems where you are guaranteed to win.
2. If you have to let your opponent go first, what are the starting configurations of gems where you are guaranteed to win?
3. If not all such configurations can be found, describe the ones found and any patterns observed.