How do iI level up in Steam Gifts

Do more giveaways.

It depends on the value of the games you giveaway and if they're bundled or not. A triple A game is more likely to raise your level than a bundled one. I also suggest you read the FAQ for more information. http://www.steamgifts.com/about/faq

There's also a CV calculator if you want to see how close you are to leveling up. http://www.sgtools.tk/

Keep doing giveaways.

Read the FAQ

Read this

And a happy cake day to you

Giving away games is the only way. Non bundled games will earn you more, but if a game has ever been bundled then you won't be able to get full value for it.

Now if you gift a game that later goes into a bundle you still keep the full CV bundle as you gave it away before it was a bundle game.