I will be playing with a player in a few days and his level (1400ish) is slightly lower than mine (1500ish). However, he is very familiar with dubious gambits and opening traps and I can easily lose the game in the first 10 moves if I am not careful. On the other hand, if I can survive the opening stage and enter a quiet and equal position, then I have good chances to win the game.
I am planning to play the London system (if I play white) and have studied some possible gambits (traps) that he may play, including the Englund gambit and Old Benoni Defense. But there are so many traps to avoid and I am not sure if I can study all of them. I have even considered starting the game with the very rare Saragossa Opening if I am planning to enter the London system anyway. Here I am asking general principles when facing unfamiliar gambits/traps.
What should I do if my opponent plays a seemingly unreasonable gambit if I am unfamiliar with this position? Is it generally safer to decline the gambit and solidify one's own position instead?
In general, how to avoid being a victim of opening traps?
What are some opening options that are relatively "safer" that one is less likely to face ambitious gambits?