Clothing is a tough market to play in. And yes, you do need quite a bit of investments (at least 1,500 EUR). Think of that money as investments, not as expenditures.
My recommendation is that you focus on branding. Building a name first, then gain exposures through social media marketings and SEO. Honestly, it's all about reputations. If you can get a group of people to wear your clothing, then a ton more will flock to your brand in due time if you keep on scaling up your marketings.
Good luck on your journey!