To learn. Your first design is your chance to cut your teeth, explore the new world of game design and learn the ropes of all the game components that are there but you took for granted. Learning is the most valuable thing (way more than money) you can take away from it.
Your first design, no matter how many times to revise it, will be rough around the edges and mechanical in nature. That’s okay. Nobody expects you to nail a homerun on the first try. Some people have. Matt Snyder’s Dust Devils is a good example, but don’t be discouraged if you don’t meet with that sort of success. Game design is a skill that requires practice and patience to improve in.
Your goal for your first design should be to create something you’re happy with. Many people may attack your work. Many more may ignore it. Some will read it, play it, and offer feedback. Listen very, very closely to them. And it’s not so much what they say about your first game specifically, but about the mistakes and areas of growth you have. Your character creation may be weak or your rewards not effective enough. Listen to what they criticize, not just how they criticize it. Often, their words will have larger implications. View game design as a holistic process, not a series of steps and requirements.
Your first game is an experiment. It really is. Sometimes those experiments turn out great! Sometimes they blow up in your face (like mine did). The important thing is to watch the experiment as it runs its course. What ingredients worked for you? Which ones need tweaking? Which ones should you leave out the next time? If it exploded, why?
Some people will say that your first will be crap game. I don’t believe that’s the only inevitable outcome. What I do believe is that your next game will likely be better. And your game after that will be even better and so on. So what I’m saying is be realistic with yourself. Put everything you have into your first design. And if it doesn’t turn out like you had hoped, dust yourself off and get back at it again. Trust me, the inspiration will come.