Affiliate Marketing Secrets

I have this clothing line idea that I have been putting together for the past 2-3 months and it is very uncommon and unique and I think it will take off (Googled, did my research. Very uncommon). Is there any advice any small business owners or small clothing line starters have that I can use on my journey? Why is it that some small clothing lines never blow up? What should I avoid? Any advice on steps to take? Timeline? Thanks