Playing around with a successful bait is the easiest way I found to learn when starting out, at least for me.
I started by taking a commercial crankbait that I liked, and copying it. I used the original to learn about lip angle and size, hardware locations, and ballasting, by floating it in a bucket of water, and then adding ballast to my bait's front treble until I got mine to hang at the same angle and depth as the original.
Once I'd figured out how to do that, I started changing the bait in different ways, and seeing how those changes affected the bait's action.
I can now make a crankbait from scratch, to run at a specific depth and with a certain action, and be really close before I take it out to fine tune it in the water, but it took lots of failures to learn what affects what, and how to correct problems.
Good luck. It's a fun ride.