Multiclassing/Dipping Shame

[Morty]

How will I know if I'm playing WELL, though? If I just follow my instincts or go for what I think is cool, I'm going to fall into the various traps laid in the rules by picking bad options, becoming a liability to the party in the process, and then no one will wanna play with me! And how will I know if I'm a good or bad roleplayer if other people don't TELL me?

The only people whose opinion matters when it comes to your roleplaying are you and people you play with. Not random people on the Internet. And unless you're actively disrupting the game or making other people uncomfortable, how exactly do you roleplay "wrong", anyway?

Trap options are a completely separate issue and, as far as I can tell, completely unrelated to the topic at hand. Not multiclassing isn't a trap option and isn't going to make you a liability.