What should I upgrade on my bike

Currently have a fully stock Java S3 and I'm looking towards upgrading anything and everything about it. But what should I start with? Which parts and what should I replace it with. I'm not sure with what clipless shoes I'm getting but I'm currently saving up for that and new pedals . Also looking forward to just accessories because I'm quite a new rider ( I started last month ). But other than that I don't know what's next. Also don't know the brands I should mainly go for when it comes to stuff like parts and accessories. Any help/recommendations are appreciated.

Edit: I'm on a budget btw if that wasn't clear, I'm just saving from my allowance.