My site need to be optimized.

Hi there,

I finished customizing my WP template and I would need support for the following os that the site performs better:
1. Remove useless resources from the theme by creating a child theme
2. Setup cache plugins & combine/minify well CSS/JS files
3. Remove 404 resources
4. Identify useful plugins and discard useless ones.
5. Whatever else that the expert may find in need to be improved (happy to listen to advice and respective quotation).

It is a simple site, just to showcase my consulting services (no shopping cart or e-commerce stuff needed). I just have no idea about how to improve the 4 points above-mentioned. Anyone could help? If positive, just get in touch and i'll provide with more details if you need them!

Thank you,
Natalia