I've always just been a singer songwriter, I play guitar and I sing..
I'm really struggling to write anything beyond s*** when it's just me and my guitar.

I'm thinking of just buying logic and having a go with my midi keyboard..
I'd need to learn some basic piano first though..

Any ideas?

Your guitar knowledge of scales, modes , chords etc will likely translate to keyboard so that’s a great start

Learning sound design and programming will most likely be your top priority

Piano

Learn to play piano write songs with a keyboard

playing music