I need levels to win?

You don't need to, but higher levels -> more giveaways to enter, also higher levels -> less entrants -> higher chance of winning.

No. The levels are a replacement for contributor values which give you access to more giveaways (if people but such restrictions on their giveaways).

Recommend you read here:

http://www.steamgifts.com/discussion/RqwrY/contributor-levels

If you give a lot of games you'll gain lvl's, which mean you can enter giveaways for people of certain lvls = more chance to win.

But yeah you can win even with lvl 0, but the chances are much lower since more people are able to enter ;D

Oh! That's why. So I need to be very lucky if I want to win something. Then I'll make some giveaways and level up. Thanks!

You do not. People with levels can enter some giveaways you can't, but if you enter a giveaway with someone at L10, they are no more likely to win than you are.