What is a better business growth strategy: selling more of the same product, expanding product offering, or both?

As you mentioned apparel is a price sensitive industry. Since you are getting a lot of inquiries, but not enough conversions, you first need to review why you are unable to convert the inquiries into customers.
Given that this is a crowded, price sensitive market place, you should also explore your differentiation and positioning.
Lastly, definitely explore other markets where you could have better conversation.

Happy to chat!

If you are acquiring customers it is ALWAYS great to have more products to sell to them. It's easier to sell to someone who has already bought from you. Expanding your product offering and selling those products to your existing customer base will drive repeat sales and go a long way to increasing predictable revenue and protect you from algorithm changes. Leveraging email marketing and properly segmenting your customer base will help you do this!

I have a mixture of all the the answers previously but the bottom line is the best growth strategy is to implement a growth process. As Sean Ellis said, "No individual growth hacker or even a growth team can outperform a company where everyone is mobilized to accelerate growth." One opinion and one action won't create growth, it is rather a mixture of first analyzing and testing EVERYTHING. Qualitative AND Quantitative questions.

You can take a free growth assessment here https://www.growthswell.com/#assessment To find out what level you are at and then it will tell you where you need to focus first based on your answers.

The first thing to do is do assess whether your conversion rate is really that low. E-commerce conversion rates are around 5% for fashion and apparel. Considering you are a startup, then it's quite reasonable that you'll be getting a far lower conversion rate than the 5% average. Here's more info on e-commerce conversion rates - https://www.smartinsights.com/ecommerce/ecommerce-analytics/ecommerce-conversion-rates/ and https://www.invespcro.com/blog/the-average-website-conversion-rate-by-industry/

If your conversion rate is really low, then you need to determine the cause. Is it pricing, product offering, targeted customers, etc.?

If your price is higher than your competitors, then try to justify that higher price before dropping it to match (sure fire way to run out of business). You don't want to race to the bottom of the price pile as existing, entrenched competitors can undercut you. So, promote your benefits (faster turnaround time, quality products, impeccable customer service, etc.). Sure, there will be customers purely shopping on price, but there will be those who are willing to pay more with adequate justification.

Maybe you are targeting the wrong customers? Take a look at your current and past customers and see if there's a particular profile that the majority of those customers share. Then focus your marketing and website on those customers.

It sounds like you are doing custom apparel and other decorated goods, such as promo items. Most customers (typically businesses) looking for promo items and corporate gifts typically like to deal with as few vendors as possible. So, you can start with your existing t-shirt customers and ask them what other products they purchase or would like to purchase. It's a lot easier to sell to existing customers than to acquire new ones.

Good luck!

It's always best to maximize sales on an existing product, before creating a new one.

This could look like increasing traffic, trying to improve conversion rates, getting affiliate partners, etc.

But start to maximize your time and investment that you created with the first product, and create a best performing funnel for all your sales.

Once you feel your current product is selling at an optimal rate, it would be smart to create a product that is an upsell, downsell or crossell to the existing offer. And then follow the same outline with it to create maximum sales and traffic.

In order to gain organic growth you should focus on expanding product offering. Variety of products will attract more people towards your brand and will increase your customer base. Selling more the same product will be a short time limited scale strategy and will not help your company to grow organically.

Growth is fundamental to a business' survival. A concrete growth strategy is more than a marketing strategy, it is a crucial cog in your business machine. Without one, you are at the mercy of a fickle consumer base and market fluctuations. Growth strategy allows companies to expand their business. Growth can be achieved by practices like adding new locations, investing in customer acquisition, or expanding a product line. A company's industry and target market influences which growth strategies it will choose. Here are some actionable tactics for achieving growth. Viral loops are not guaranteed to go viral, and they have become less effective as they have become more commonplace. Some of the growth strategies are as follows:
1. Word-of-Mouth
From just 8,000 users at launch in 2013, Slack hit one million daily active users in late 2015. That is a stellar growth metric. In the beginning, Slack made itself available to large, established companies like Rdio and Flickr, generating plenty of early press coverage. The company focused on user satisfaction above all, answering thousands of helps tickets and tweets each month. This attention to customer service led directly to positive word-of-mouth amongst its early adopters. In 2014, co-founder Steward Butterfield stated, “The growth has been completely insane and almost entirely on word of mouth.” “In fact, we just hired our first marketing person, but he doesn't begin until next week”. “That’s why social proof remains the #1 instrument in both sales’ copywriting and overall marketing content, and that's why most brands draw focus toward their online reputation.” Focus on delivering a spectacular user experience, and users will spread the word for you.
2. WhatsApp
Over 1.2 billion monthly active users can vouch for that. Its founders, Brian Acton and Jan Koum, wanted to create a product without the baggage that came with similar apps at the time. They intentionally opted for no ads, no marketing, and a free first year to attract users fed up with other providers. WhatsApp stood out by being dramatically different from every other option at the time. They created a product that was brilliantly simple for sending and receiving instant messages.
3. Growth Hackers
Highlight what you find, and get users talking.

4. In-Person Outreach
According to an annual report from their parent group, Match Group, Tinder raked in over $800 million in direct revenue in 2018. An excellent growth strategy and a lot of dedication made it happen. Tinder’s growth strategy took off at the University of Southern California in 2013. Tinder paid for the whole event. The company also hired a bouncer, and any student who wanted to get into the party had to download Tinder at the door. Once those students returned home from the party and started matching with each other, Tinder became what co-founder Sean Rad describes as “a phenomenon within USC”. Over the next few months, the Tinder team conducted more personal outreach at fraternities and sororities across Southern California. This set the course for Tinder to be carried by word of mouth.
Besides if you do have any questions give me a call: https://clarity.fm/joy-brotonath