Basic needs are nothing more than pins, thread, bobbins, needles and the time to practice. My LA came with the ruler base as part of the package but if yours did not you may want to consider getting one if you think you will end up getting LA templates and rulers and using them.
I think you will find as you get to know your LA you may want to try different things, like pantos, templates, rulers etc. First time I tried ruler work I found it awkward and difficult to adjust to but as with all things LA practice made me quite proficient with it. Now I rarely do any quilt with at least some SID ruler work. My first ruler was a simple 6" x 3" one. I have since gotten a set of circles (ranging from 2" to 10"), a longer ruler a spiral template, several curved rulers for curved crosshatching (you can do lots of other cool things with them too) and a clamshell template. I bought a couple of pantos and quickly realized I am not a big fan of pantos but you can't beat them for whipping out a very quick quilt job that usually looks fantastic.
I used to think prewound bobbins were an indulgence. Now I consider them a necessity and I prefer prewounds to anything I wind myself. Especially magnaglide prewounds.
I use my open toe foot for everything. I don't bother to swap out the hopping foot for different tasks. My open toe works just fine with everything for me.
I am still pinning my quilts to my leaders. I haven't yet invested in the red snappers but am considering them. Books. Hmmm. As Dunster said different books for different people. I focus on ones that give me ideas for motifs, like Karen McTavish (which usually come with a bonus CD to watch). Eventually I will probably invest in micro handles for micro work.
Just remember, no book or gadget will improve your skills immediately. The only thing that does that is using your LA and having fun with it. Everything else is just inspiration IMHO.