What WOW expansions do you need? (Answer)please

You have to start with the original (Vanilla) World of Warcraft. That basically takes you up to level 60. Then there is Burning Crusade That gives you story from 60-70 Next Wrath of the Lich King from 70-80. Then it is Cataclysm from 80-85.

You HAVE to buy and play them in that order.

Why not try a 15 day (up to lvl 20 iirc) trial and see if it is for you first?

Start off with the plain WoW. When you hit level 60, upgrade to Burning Crusade/Wrath of the Lich King. You don't need it before that. At 65/70, get Cataclysm. You can get it sooner if you want.

More important than actual game expansions, at your level, are UI expansions. Download WoWMatrix. It's a UI add-on manager. From there, download things that come in handy. For example, if you're telling people your coordinates, get the Coordinates addon. There are also addons for telling you where loot is, how many soul shards you have, and your stats v. the people in the area. Your UI will become more and more unique as you level, and it'll be a great benefit to you. Eventually, nobody will be able to tell that you're playing WoW, your UI will be so different! All serious WoW players follow that path. I recommend you do so as well.

I would make an account and search or ask on their forums for it, here

I don't know if the forum there is like in League of Legends, but in LoL we have an amazing forum w/ community that solve questions like your regarding the game :)