This is Dallas from the Shopify Social Care Team.
This is so exciting, and I'd be honored to help you get your store set up.
I did some looking on the themes to see what ones would work for you and I was able to find a list that I think would be worth scanning through. This is the link to the "Clothing & Fashion" themes. Obviously you're able to use any theme you want, but these have features that you might find beneficial.
Can you tell me a bit about your store? What kind of clothing items are you selling? Do you have a lot of items or do you have a small catalog? There are some filters you can check down the side of the page on the left-hand side, but if you give me some insight I can see what I can do to help you narrow down your options.
I have this link here which has some success stories of stores that use Shopify for their sales. Since they are words from other business owners like yourself there might be some inspiration in there for you.
2. Now lets talk shipping.
There are basically two steps to this process: Figuring out the prices that you're going to charge and then buying the shipping labels after the items have been bought by your customer
For shipping rates, you can either add the rates in the checkout or you can add the rates into the price of the product so you can advertise free shipping. Honestly, that is the option that I suggest. It not only simplifies your life by avoiding the process of setting up weight-based shipping rates or price based shipping rates, but it also presents as a buying incentive for your customers. People love free things so why not give them to them am I right? Especially since you aren't going to lose any money from it.
If you didn't want to go with the free shipping route another option for simplifying the shipping option would be to add third-party carrier calculated shipping rates. This would basically make it so that your customers would see the real-time rate of what the shipping will cost at the post office when you purchase the labels so that you're not playing a guessing game.
Then when you go to buy the shipping labels I suggest that you use Shopify Shipping since you're shipping from the USA. Shopify Shipping basically makes it so that you can buy shipping labels right in your admin so that you can save time at the post office. I can tell you first hand that that saves so much time! I used it with my business and it was a lifesaver time-wise.
3. Finally, payment plans.
Before I bombard you with all of your payment gateway options in the USA or I give you information on our Shopify plans can you clarify what you're looking for? Are you wanting to know what you would pay or are you wanting information for how your customers would pay?
I sincerely look forward to gathering more information about your store so I can help you further.