How to start a online business with low budget

www.tray.sg is an online boutique.

it is an online blogshop based in Singapore. the direction is to be like the brand AMENPAPA.com.

is there any way to promote the website on a low budget? (besides social media)
any way to source out manufacturer for womenswear and menswear?
any way to reach out to the target audience of 18-30 year old?
what is the more specified direction?
is there a way to test out if the design is sellable before manufacturing?