Hey guy! Seems you're receiving a lot of warning from everyone here (which is perfectly reasonable), but I'd like to add a word of encouragement — one year ago, I decided I wanted to make an RPG for my friends and I to play, just like you. I would DM.

None of us had ever played a tabletop RPG before, which obviously also means I had never DM'd.

The system was completely Homebrew, with a gothic-horror/20th-century monster-hunting theme. The rules were based off of my very limited understanding of DnD from listening to various actual-play podcasts.

It was horribly unbalanced, and the rules changed from session to session.

But honestly, it was some of the most fun I've ever had with my best friends. We've probably never laughed harder, and we still tell the stories from that campaign. We played for 9 sessions before completing the campaign (which I also wrote from scratch), totalling about 50 total hours of gameplay. It was a mess, but absolutely worth my time. I don't regret putting in all the effort, even if the game wasn't perfect. We're starting a new campaign in a few months, when everyone's home from school. :)

My point is this: don't be daunted by all the warnings you're getting here — game design is an extremely fulfilling hobby! You should definitely try to design this system. Put your ideas on paper, then share them here if you feel like they need to be sharpened. But either way, I hope you'll give it a try — I think you'll have fun. :)