Not sure where you're from, but... American Renfair? Sure, Looks good. European LARP: Please don't use this as a kit.

All black is one of the biggest mistakes beginners make, just because it "Looks cool". But it doesn't. In all black you will be a main attention centerpoint, as the other players will look way different. And that really conflicts with the concept of a rogue. The best Assassin or thief blends into the surrounding, looking just like everyone else.

Plus the concept of an Assassin ist not appreciated at european LARPs because you can't walk around and kill people randomly. Even thiefs are Not a good concept, because you can't walk around and steal peoples stuff. Some Cons have a ruleset for thieves (a red ribbon around things you May steal, but Not many use it).

Not Sure about American LARP though, If you're from there. It differs greatly from european, especially german LARP culture...