Is there like a step by step or typical order of operations for designing a TTRPG?

Like, is there something thats so fundamental that its considered the "starting point" and if so, where do you go from there?

Ive never made a ttrpg before, but I have an idea and Id like to give it a go. I just dont know where to start and I dont wanna start in the middle and then find out I have to go back and figure out other things, and then revise the things I wrongly did first, etc.