I myself only have about 2 weeks experience on the FISD forums and am still considered a "newbie." I would recomend a couple of things from what I have learned.
1) Find your local garrison (can do this by going onto the 501st Vaders Fist website). They will be able to help you for sure. And, on another plus side, should be in your local area. That way you can attend any upcoming events and meet the members in person. That would be an ideal time for questions.
2) From what I have heard and read, an FX kit is good for someone who is a beginner and strapped for cash. From what I understand 85-90% of the legion wears FX armor and it is accepted. If you want to upgrade or "mod" your armor it is possible to do so. There are other armor types out there such as: AP, AM (a more specific FX type),
but as I mentioned before I am still new and learning the differences.
3) Some of the acronyms you will see floating around: TK (Stormtrooper), TKC (Stormtrooper Commander), EIB (Expert Infantry Badge)
Don't be afraid to ask any question, no matter how minor. It could save you money in the end. READ READ READ everything you can find among the forums.
I hope this was at least some help and if you have any questions please don't hesitate.
Josh