Hey everyone, I'm a noob on this forum, so sorry for any misguided ignorance.
I suppose Im in a unique situation (the Japanese learning stats that I have) for myself, so I didnt check if anyone has asked my question because they probably haven't.
I have been working through japaneselevelup.com's kanji deck in which RTK 1 and 3 are combined into about 1900 kanji that are the most useful out of all 3000+.
I am using the Reviewing the Kanji website to learn as well as review, so to finish the deck will be fairly simple.
My question is however, after I finish this deck of combined kanji, what should I do?

Background for myself:
I grew up in Japan; as well as speak pretty basic, but I suppose pretty useable Japanese with my family at home, so I have a natural understanding (but not in-depth knowledge, i.e. names of rules) of grammar. My pronunciation is not flawless but pretty good as well. Grammar, pronunciation, and understanding (hearing) Japanese are my biggest strong points. However, because I never really bothered to engage in learning Japanese till now, these are the things that I must improve on:

1. Learning more vocabulary to use with my good grammar (to have more intelligent conversation, understand more complex readings)
2. Learning the writing system well (kanji in this case)
3. After learning the individual kanji, learn compounds and readings
That being said, I have not started any kind of vocab/sentence deck. I only have my combined anki deck and that's it.

So to go more in depth with my question, I would like to ask you guys, who Im sure are very experienced, what I should start with in my situation. I have around 800 kanji down right now, but most readings I dont know, and my vocabulary is fairly simple. Maybe around 1000-2000 words. Also, I have access to lots of legit Japanese material. Light novels, actual novels, manga, anime, that sort of thing. As well as access to many dictionaries.
Any Anki decks you recommend? Systems? Ways to learn? After my 1900 kanji deck, where should I go to get to around 3000+ proficiency while learning readings at the same time? Thanks for the help everybody.

Your question is actually fairly common. It sort of reads as "what should I do after RTK?"

Most people seem to leap into core 6k to core 10k vocabulary decks while ignoring the readings altogether. The thought behind that is you gain an understanding of kanji readings as you increase your vocabulary and read native materials. That way you won't have to allot more time to learning individual readings.

The vocabulary decks also tend to have sentences coinciding with them, so that might even give you a gateway into more advanced sentences.

As for writing, RTK covers learning how to write, as does learning the kanji radicals and practicing writing in itself.

Lucky you! If you already have a good spoken Japanese, chances are you could pick up easy books right after learning your kanji deck. Are you very good with hiragana/katakana?

At this point it's really about what you want to learn I guess. Core6k is one option, I went for frequency lists... but you could also simply add the words you don't know while you read. I like to test those two directions, but it's really just me: side A kanji + meaning, side B reading in kana.

You know your situation the best so try a bit of every method and find what you like the most!

You should understand what you want to do in Japanese. Do you want to converse, read, watch Japanese TV..? It sounds like you have a leg up on most of us here so you should try to leverage what you know. It sounds like you can already do a few things in Japanese. If you can already follow along with talk shows and dramas, that would be good practice. Subs2srs might be a good companion to this. If you are interested in conversing, maybe make an http://italki.com account or just start talking with your relatives in Japanese. The point is to practice doing what you want to get better at.

If you don't quite have the vocabulary to follow dramas or the kanji to read easy material, well then you need to study those things. Core is good for building vocabulary and RTK is great for learning kanji. But try to graduate to actually using the language as soon as you can and study kanji and vocab as a supplement to that.

If I were you, I'd fill in the gaps with websites like lang-8 (write diaries in Japanese and native speakers will correct you), and maybe podcasts like Japanesepod 101. Though I started from scratch, these two things helped me gain fluency over all the other things I did.