Jisho

not worth imo, you can't find many idioms or slang on the 電子辞書

That's not what I am saying, I'm talking about the physical device.

https://ja.wikipedia.org/wiki/%E9%9B%BB%E5%AD%90%E8%BE%9E%E6%9B%B8

I can see how an electronic dictionary might not have much slang, but I don't see why it would be lacking in idioms. Many electronic dictionaries have numerous dictionary datasets in them, including very comprehensive ones like Kojien.

I would say the value to you would be determined by how much you feel like you're going to appreciate having all those premium dictionaries in one place. If you don't care about which dictionary you're using, then just accessing free monolingual dictionaries on a smartphone you already own would probably be better.

If you don't mind spending money, my personal favorite is https://www.monokakido.jp/ja/dictionaries/index.html

i think itd be worth it and fun