So if it's not something I should be concerned about till 50, why are there vendors in places (I.E. Coruscant - sorry if I murder the spelling of that world!) for lower level players with items for sale marketed to said lower levels?
Sorry, this is a bit confusing for me. When looking at the items in the store, it shows tiny little icons in the lower right signifying how much it costs - the problem is, hovering your mouse over these little icons doesn't tell you what they are. So you're left guessing (if you aren't already familiar with them) what in the world you need to buy the gear.
The Reason for the vendors to be on a fairly low-level-planet is this: they are not primarily targeted to new players with their very first char, but to not-so-new-players who want to get gear for their twinks.
You will get the birthright-token or whatever they're called during your storyline, but somewhat too late for you to really need the gear. Instead, you can use those token to buy gear for your next char.
But, in my opinion, you can save yourself the trouble alltogether. You see, the gear you see on the vendors may be bette rthan your current gear, but it will only be better for maybe 5 levels. Afterwards, you will get even better gear from mission rewards and other vendors. Plus, the legacy-vendor-gear, although beeing bound-to-legacy, is also bound to certain classes, so, if you would buy it for you now, then only other chars of the same class/advanced class could benefit from it. So unless you plan on playing the same class more than once, think twice about the legacy gear.
I have gathered a lot of those tokens, and have never used one if them.