A lot of businesses take advantage of social media as a form of free marketing since it will not cost you anything to sign up for social media accounts. However, if you want your clothing brand to compete with other established brands out there then you might have to spend money for marketing schemes. Allot a few dollars for ads, which are mostly spent online in Google, Facebook, Instagram and co these days. You can also give out shirt samples to a few friends and target customers to spread awareness of your brand.
No matter how you advertise yourself, shell out some money for your marketing campaign if you do not simply want to rely on free marketing that the internet and your friends can provide. Spending on marketing is not necessary, but it certainly helps your how to start a clothing business venture. Learn how you can go viral as for instance Patagonia did with their "don't buy this jacket" campaign.