Need some tips for getting ranked higher in ecommerce

Hey i have a webshop selling perfume samples in the netherlands. I have been making progress with seo. My home page gets ranked r2 on few different keywords (but similar). Like parfum samples / parfum testers etc. But my home page only mostly gets ranked not my product category pages. Everytime i make a specific page for that keyword it gets indexed but my home page after a while takes the index/rank for that keyword and the specific page disappears from google. Because i can't seem to be able to rank my category pages i just started adding seo on my homepage. To my suprise i ranked r1 on a keyword yesterday with my home page. Added a few more texts and changed some words to some keywords so it would rank higher on other keywords aswell. But it got changed to r2 again with every keyword.

I am not really sure what i should do to get more traction to my website, thinking about just investing into google ads. Do you guys have any tips i could improve on? thanks!