learn the hiragana and katakana, then focus on the spoken language and maybe like 100-200 common kanji, then when you feel like you're fluent learn the written language

I think all languages are better learned with speech first, and then learning how to read and write later. The reason is this: We have our own conceptions of how a certain word sounds like based on what we see. Therefore, you will use your initial concepts of 'ri' when you see the word 'ri' and then that sound might be stuck forever in your head. If you start off with learning the sound, and then later on you figure out how it's written on paper, your speaking will be more accurate than if you had started with reading and writing. This is demonstrated here in this TED clip: https://www.youtube.com/watch?v=-WLHr1_EVtQ

This actually depends on what your reason is for learning Japanese. I agree with the other replies about hiragana, katakana and the first 100/200 kanji being essential to your learning. If you want to go study for the JLPT, or if you want to translate at some point, then it would be best to start with reading and writing first. If you are not planning on using Japanese much when it comes to reading or writing, then it could be better to focus on listening and speaking first. Personally, I would recommend doing all of it, even if you mainly focus on one or two aspects. For example, if you choose to focus on speaking and listening, you can also learn some extra kanji from time to time. Or if you learn to read and write, it could be very useful to study vocabulary as well as having some listening practice. However, I would recommend not to neglect any of the aspects completely.

I agree with Justin that hiragana and katakana are essential. Learning Japanese by sound for you is not ideal. The human brain past the critical language acquisition period cannot learn new words/grammar fast. Thus, if you choose this route, it will take a very long time. Adults compensate this by having a higher rate of vocabulary memorization. Therefore, it is best that you don't give up your strongest weapon. In addition, your exposure to interactive Japanese is probably minimal. Every time you successfully recall a word, the word becomes more accessible in the future. This means that triggers that urge you to recall is a vital component of learning. Passive listening cannot consistently evoke these triggers in large frequency that urges you to recall. Thus, text material that quizzes you is too much of a valuable asset to neglect. My recommendation is do all simultaneously. Listening, reading, speaking, and writing.