It's best to start by building / learning from other people's “know-to-be-good” circuits before you endeavor in developing your own. Eventually, you'll begin to see all these circuits as nothing more than pieces of a jigsaw puzzle. The jigsaw being your "target", your end-goal, where you will collate the pieces that you gather, modify, or develop over time. No point reinventing the wheel unless needed.

Best of luck with it.