Bundles / Packs / Collections vs. "Don't enter for games you already own."

I don't think you're forbidden to, but the owner of the giveaway usually specifies, such as not being able to enter if you have more than 2, more than half, etc.

Let's put it this way: You are not forbidden to enter it (unless it's a "GOTY" bundle, and you already have the base game and want to enter for the DLC).

This way you can't go wrong: ask the giveaway creator if it's okay to enter.

It depends on the giveaway maker, most times he puts in the descrition how many games you can have to enter. When he doesn't say anything in the description then ask him if you are allowed to enter, it's never nice (and the giveawayer can request a reroll) when you own many games from the bundle.

It's up to the giveaway creator, if you can enter the giveaway or not. That has been stated by support several times. You should ask in the comments of the giveaway, if it's okay to enter.

When entering, write have you have the base game or the DLC, and see if the creator answers you.
If he don't answer and you win the giveaway, ask again.

It would suck if you won and the creator rerolls though. I would feel so excited for winning, then be sad.

Well, If I was missing a few of the games, and I really wanted them, then I might enter.

I would feel bad to waste a nice game...