Ok. I'll try to keep this short, and I say this because I have a bit of history.
I started piano when I was 5 years old. I attempted composing at age 15 but with no mentorship, I grew frustrated and put it on hold.
I picked up guitar in my early 20s and started writing songs for a band. When my bandmates heard me improvising on piano, they said it sounded like videogame music.
I started composing pieces by first recording on a tape player and then playing the tape back while playing the next part on my instrument. From there, I experimented with my friend's 4 track recorder and eventually started working on a PC that was a build using a bunch of old components. Using a cracked copy of Cubase vst32, I began to learn how to sequence and record.
I decided toward the end of my first university degree that I wanted to study music in university so I picked up the piano lessons again, re-learned how to read notes, took theory, and got my application together. I learned how to use finale, created music scores, and got my friends to record my music.
From there, I did a Bachelors, Masters, and Doctorate in music composition and I learned the Cello as well. I played in university orchestras for four years during that time.
During my doctorate, I took a 'composing for film' course and I scored animations created by sheridan animation students:
https://vimeo.com/23246965https://vimeo.com/64578469At this point, I purchased a legal copy of Cubase 6 and East West Quantum Leap Symphony Orchestra Gold and I started working on sequencing again.
I finished my Doctorate in 2014 and then started trying to work on my media composition portfolio. I've done a few professional gigs since then, film, games, and concert music as well. I've also been spending this past year studying audio production and mixing to bring my production ability up to a level that is somewhat comparable with my composition chops.
My thoughts: To create serious music is a lifelong and very demanding skill. It takes hours of work and study, especially if you want to work with live player. Orchestral music, in particular, is challenging to write if you desire for your composition to be heard in a live / acoustic environment. But my goal was to be a superlative composer and I wanted to do music on a very serious level so I had to make that investment.
When it comes to media composition and -in particular- games, the background of the composers and the limitations of the technology have created an aesthetic in and of itself. So really, the only real 'rule' is whether or not it 'sounds good'. You don't have to consider how your idea will translate onto an actual instrument and whether or not it will be playable, or sound the way you want.
So, it's easier somehow.
To start: I suggest spending time playing an instrument. Pick one. Also, 'just write' is good advice. The only way to start improving is by doing. Write a melody. Write chords. See how the different sounds work together. And, HAVE FUN!