making a custom rom from fire-red in pksv *I've never made a rom and need help*

[Pockettobeau]

I'm trying to make a whole custom game with a small number of custom evos, I want to add mega evolution and custom mega evolution, i am striving towards making a whole game with custom everything while retaining all pokemon not passed oras

I also need to know any place to make custom sprites and tiles


any tips would be helpful since I've never done roms or coding

I'm using Fire Red as the base and pksv with advance map

if i shouldn't use fire red as the base please tell me