I would say you should start by having a website. That's pretty much a no-brainer -- a website gives you something to promote on Facebook, Twitter and Pinterest. Plus, if someone wants to visit your brick-and-mortar location, the first thing many of them will try to do is look up your address and hours of operation on a website. Having an attractive and functional website is one of the hallmarks of a "real" business.
Whether this means you spend money on hiring a professional or whether you do it yourself using something like Wordpress and one of the many ecommerce plugins available depends on your level of comfort and expertise in web site design/optimization, and how much time you have available versus how much money you have ready to invest in business development.
(In other words, you're going to pay either way: with your time or with your money...)
I wouldn't spend tons of money on hiring top-of-the-line photographers, especially to take pictures of one of a kind stock that will only be used as long as you have that item in inventory. But you do need good quality product images if you want to sell online. Again, it comes down to your comfort level, what equipment you have yourself (or can borrow from a friend) and how much money you have available to invest.
There are a number of online tutorials on how to take good product images (look for tutorials on how to photograph products to sell on eBay, for instance). Even with a point and shoot camera, with a bit of planning and care (and a touch of Photoshop), you should be able to produce web-quality pictures yourself, if you're so inclined.
Otherwise, maybe consider hiring photography students? They get to build their portfolio and you get high quality photography without spending a fortune.
I would also begin immediately building relationships with vendors. Imagine what might happen if your business takes off faster than you planned. Suddenly, you could find yourself without stock in hand as you scramble to locate vendors... you don't want to lose momentum by presenting your website visitors with a lot of "out of stock" notices, or turn away customers from your store because of empty shelves and racks.
This is not to say that you load up on tons of stock right away. Buy what you can, what fits with your budget and business plan. But start building those relationships, so when your business does start to take off you'll be ready.
Social media (and other marketing and advertising tactics) should wait until you're ready to open the store and your website is ready to go live. In the first place, you don't want to invest in getting people all excited about shopping somewhere that isn't going to be open for awhile.
It's OK to do some "teaser" promotions during the week or two leading up to the store (and website) grand opening, but don't go crazy with it. You want to be sure you don't blow your budget on "pre-opening" teasers and leave yourself with nothing to promote the store after it's open.
I would hold off on staff and warehouse/office space until after the business is open and you see how things are going. (Assuming you have enough space to keep your existing stock in your home/apartment, or can rent a small secure garage or storage area month-to-month, or something similarly inexpensive.) The bankruptcy court archives are littered with stories of startups that raced to hire staff and outfit offices before their business sales volume really justified it.
You will want to start networking with potential employees, the same as you would start networking with future vendors. And you might want to scout out neighborhoods that might be suitable for combination warehouse/office space (likely more economical than separate locations for each). That way, you can potentially more easily hire appropriate people and locate appropriate space quickly when the time comes. But don't rush to lock yourself in to these sorts of longer-term fixed expenses before you have to.
One person I know who recently retired from a highly successful business started out doing it all by herself, working out of a home office. Then she hired a virtual assistant... then a "real life" full time assistant who would come to her house to work in her home office. Eventually, she hired additional staff and rented office space in town. Later, as she decided to wind down the business, she let the staff go (or simply didn't replace those who moved on to jobs with other companies) and moved the business back to her home office.
The point is, she made sure the business had the resources needed to succeed, but she didn't over-spend by tying up a lot of money in unnecessary office space or staff.
Best of luck with your new venture!