You've made a huge mistake
"The dumbest mistake is viewing design as something you do at the end of the process to ‘tidy up’ the mess, as opposed to understanding it’s a ‘day one’ issue and part of everything."
— Tom Peters
True. The first part of the design process is learning about you, your business, your business goals for the project, your audience, what they care about, and what you want them to think, feel or do as a result of the design.
It would seem that you couldn't even decide what form your idea should take until you take all of this into account. And so it goes with all subsequent design decisions.
Design is crafting an idea that fulfills a purpose toward achieving a goal, and it can't be effective if it isn't thinking of all of these aspects & expectations.
I think most people assume design is simply a wrapper that gets tacked on at the end. But that is really just a clean-up job. And maybe that's all that's needed, but make sure that's true before forging ahead. It's fine to make that choice if you understand the difference between design and tidying up.