Calling yourself a level designer is tough. It’s a soft skill that you can’t prove easily like art or programming. It’s far more psychological and subjective than that. That is to say, an artist creates visuals and a programmer creates gameplay. If the game looks good and plays well, these two departments have done their job. But what about level designers? Sure, you can judge based on the difficulty of the level or the ability to complete it (hopefully without the use of cheats), but the goal in level design is to evoke various emotions from the player at specific times in the game – usually to line up with story elements – while using the game’s mechanics to their fullest potential.
Level design is playing with virtual Lego
Think of the Lego creations you made as a kid – the ones where you used your imagination to create something (i.e., not from an instruction book). How many of those would you call portfolio worthy? Probably not a whole lot of them. Either because you were 7 years old and had a much better imagination back then, or because you were 7 years old and you had no idea what level design was.
This should go without saying, but creativity and imagination are valuable resources in the video game industry. But they must be accompanied by humility and the ability to accept criticism. “This is my creation, and it’s perfect!” will not help you find or keep a job. Iteration is a constant in game design, and very much level design as well. I’ve created levels that have gone through dozens of iterations, and still feel like they need improvement.