But as a complete newbie, my problem is, where do I start? Do I simply order small quantities of random varieties from a store or website (which one?) and try brewing them at home? Or can there be a more structured approach to it? Should I first concentrate on one major type, say green tea, or jump headlong into a variety? I don't possess a tea kettle or a pot; would that be a pre-requisite or can I work with makeshift equipment till I'm more seriously into this exploration?
At this time, I probably don't even know enough to ask all the right questions, but I do want to begin, and am not sure how...

Where to start? I'd advise tasting broadly, and then narrowing in on what you find you like. Adagio Tea used to have a fabulous tea sampler of the month club where they sent along five samples of about an ounce each month, and the teas that got sent were really enlightening about how different teas can be. I don't think they do it any more, sadly, but they do sell sample assortments. Upton Tea does samples, but in my experience years ago, Adagio offered better value in the samples than Upton did.
I'd advise not sticking with just one retailer, but to sample as broadly as you can. However, bricks and mortar tea shops may offer tastings, but I find that even though they know how their teas are supposed to be prepared, they don't have equipment to implement it themselves... hence I've been told to steep green teas at 180, and then offered a sample made with freshly boiled water because that is what the in-store water heating apparatus made. Suboptimal to say the least.
Five years ago, Central Market did not have an impressive tea program... Whole Foods was much better... at least in Austin.
Teapots and kettles are not absolutely required, but a thermometer and a strainer are. Use a mug to brew the tea in at the right temperature, then strain it into another after it is done steeping. Or use a tea ball.
You might also get started exploring black teas with the imported British blends in tea bags, which are usually very hearty Assam blends that can be made with just boiled water and are often available in specialty markets in the US. Furthermore, I'd advise you ignore the directions when trying Darjeelings, as they often tell you to use just boiled water, and I find that to be too hot... I prefer Darjeelings done with 180-185ish water...
Good luck and happy hunting.