Label all the things in your room/house in Japanese with sticky notes (with parent/guardian permission) Then actually say the word out loud when you use it.
Write a short story about someone/Something.
+Describe the character(s) and/or setting(s)
+What happens in the story? Is there a problem? How is it solved?
Every day write a little bit about what you did, or what happened in Japanese. It doesn’t have to be fancy, nor does it have to be perfect grammar. The idea is just to practice writing in hiragana and get used to expressing your thoughts and events more easily.
-As a challenge you could pick a word or a few that you are trying to learn or review and make sure you use them as much as possible to help you remember them/get used to them.
This company sells fantastic flashcards if you prefer physical ones. They also have posters and graded readers.
Genki textbooks are used widely as a useful resource for learning Japanese. They come in 2 levels and there are textbook and workbook variants for each.
If you are interested in studying for the JLPT (Japanese Language Proficiency Test Link) these area very useful resource. They are split into study categories to help you focus on specific areas of the exams and come in levels based on JLPT levels. N4 being the lowest they offer, going up to N1.