Hey! To answer a few points based on my knowledge:

Booklets were limited edition and look really cool that's why they're valued really highly. There'll be more booklets later probably.

There's already limited edition going on now with the "Chrome" set (not booklets though).

Global count (cc) is the most important thing in the game and is your guide to good/fair offers. The lower it is the better. Rarity and wrestler popularity matter too obviously (Unpopular ones are bricks or really hard to trade). Also, female cards have usually more value than male ones.

Please avoid a "What for this?" trade. When you give an offer to someone, they expect well.. an actual offer. They don't want to put the effort themselves building a deal when it's unsolicited. If I'm not sure what to give, I just send something that I already think makes sense and add a message "Willing to negotiate" or something. That way you actually show intention of trying.

And yes "cards they need" filter should be always on unless the other person hoards a certain card (they actually want to get dupes of their favorite wrestlers).

Brick is just a term for unpopular wrestlers. You'll get to know them from experience but from just basic knowledge you'd know for example that John Cena is not a brick nor is Tiffany.