HP/MP individual curve

Oh ok. But, you know, I don't really know what are bytes. I mean, I kind of know this is related to memory but I have no idea how to work or think with them.

A byte is 8 bits (0 or 1) regrouped together forming an hexadecimal number between 0x00 and 0xFF (0 to 255). The binary data (or code) of a ROM in a hex editor is represented under the hexadecimal form, one number being one byte.

I prefer the 2nd choice but if it's too complicated I'll go for the 1st.

It all depends if you want to learn basic ASM coding and adapt the existing hack in the way GrayShadow suggested. If you want an easy and already made solution, go with the first option. If you want to learn stuff and have a challenge, read some ASM documentation (available on this site) and study that hack.