How to avoid falling into unfamiliar traps in the opening stage? 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 &quot;safer&quot; that one is less likely to face ambitious gambits?
As a practical matter, if you're playing to win, and you encounter a gambit you haven't seen before, don't take the material. Play defensively. This will be sub-optimal by engine standards, but will usually lead to a position that is easier to play. This is particularly true in your case, where you expect to outplay your lower rated opponent given enough time on the board.
That said, personally, at ~2100 Lichess Rapid, I almost always accept gambits, even if I'm unfamiliar with them, because it gives me good experience trying to stubbornly hang onto the material or punish my opponent's shaky position, And then, when I inevitably lose to some silly line that I never studied, I analyze it after the game, and try to remember the refutation next time. This is how I've treated the King's Gambit, and I'm slowly getting better at refuting it. I don't care much about winning or losing a single game, if I can learn from it and improve.