How to improve the level?

Give away stuff.
Longer answer can be found under Help -> FAQ

Give away games to a loving home.

Don't expect to get anything substantial out of gaining levels, just try to have fun along the way.

Also, you dont get increase in level if you give away games that have been free
Two stars ** besides the name of the game when creating the giveaway shows you which games have been free.

https://www.steamgifts.com/about/faq

Read it, its very helpfull.