Beginner at learning Japanese - when would you use certain kanji and when would you just use hiragana?

I have been attempting to learn Japanese, and I started by getting comfortable with hiragana and pretty comfy with katakana. I can write basic sentences and know a fair bit of vocab, so I started my kanji journey.

I started with this recommended book called Remembering the Kanji but I got ahead of myself and decided to make flash cards of all the words I knew already, and looked up the kanji for all of those just so I could get familiar. And boy am I overwhemeled!

So basically my question is: when do you want to use the kanji? I get that it can be a faster way to write/read long strings of hiragana. Like for university I can see it being easier to write 大学 instead of だいがく but for a super easy word in hiragana like afternoon as ごご why would you bother writing this madness: 午後 ?

I heard that writing too much kanji makes you look like you re trying to hard to sound smart and looks cluttered but too much hiragana is too hard to read.... I don t seem to be getting the idea of how people use these two together. Please shed some knowledge on this for me!