My suggestion (I've built quite a few basses at this point):
Start with cheaper parts - Rosser, etc. Build something that you think you'll like. You'll be wrong, but probably not that wrong. Expect to change parts, try things, etc. After a while, when you know what you REALLY like, try Warmoth - their necks and bodies are very well made, and you can get a staggering array of options. Their stuff costs more, but when you know you're making something you'll want to keep, their parts are very much worth it.
Start with cheaper parts - Rosser, etc. Build something that you think you'll like. You'll be wrong, but probably not that wrong. Expect to change parts, try things, etc. After a while, when you know what you REALLY like, try Warmoth - their necks and bodies are very well made, and you can get a staggering array of options. Their stuff costs more, but when you know you're making something you'll want to keep, their parts are very much worth it.