As a former COO of the leading European design agency I am familiar with this topic. We started super-small and then become one of the most influential companies of its kind. All in 10 years.

What has been mentioned in the answers above is true. Testimonials and Referrals from happy clients are always the key and you should have them no matter what.

Although, the tools and channels I have seen working the best along with providing quality services were:

• Publishing extensive amount of work on social networks for designers
• Speaking on conferences about the latest trends
• Running very specific and targeted online campaigns via AdWords and Facebook.
• Winning awards for the work

If you would like to know more, let me know.

Regards, Filip

Your Product page is your Landing page. But not the only one.

You should give it a try and create landing page for a category or sub-category (i.e. women winter collection - just guessing what it might be) where you present the products in different way than it's usually possible with standard e-commerce product page (videos, animation, story telling, video testimonials, interactive elements etc.).

Then evaluate the New Landing page performance compared to standard Product page (but make sure it's still optimized and treated as Landing page).

My suggestion would be leaning towards the simplification of the process. Require only very basic data (i.e. email) and let the user to have a great first experience with your product without unnecessary friction. (I strongly recommend FB or Google signup makes it one-step process and you get much more than just an email.)
To build the quality of your user database, you can ask for more details later. It's always a good practice to offer something in exchange, i.e. if user has 100% profile completion you benefit them with premium feature for certain period of time. Engaged users will take action. Not-engaged users will at least look good on paper and perhaps tells you more about your acquisition activities. If acquisition part of the product funnel works, then shift your focus to on-boarding and retention.
I don't want to say that capturing more data at the beginning and maintaining quality is not a goof approach. But it's likely to require more marketing efforts (both time and money) and that is a showstopper for many startups. But if have other channels how you drive the traffic and the brand is already established, than it may work.

I hope this answer will help you. Let me know what decision you have made.
Also, please feel free to reach out.

Regards,
Filip