How to continue learning japanese

You can start earlier if you want. Most things teaching grammar will give you the readings and meanings for any words they use.

Then maybe you want to use Bunpro which is an SRS for grammar? You will want to supplement the Bunpro lessons with the additional readings, etc. that they provide for each of the grammar items. They even have learning paths based on whether you are using Minna no Nihongo, Genki, Tobira, Tae Kim, etc.

For a list of resources in general, this is fairly exhaustive: