If you haven't bought any of the campaigns yet, I'd look into the Platinum edition(s) and the Trilogy edition. Trilogy edition has all 3 campaigns (but not eye of the north)
Also, out of the two "Platinum" editions, the Factions Platinum edition is the wiser choice IMO because it includes Prophecies and Factions, plus the Bonus Mission Pack for free. (9.99 value) Another reason why I like this, is because the Bonus Mission pack grants 500g every time you complete one of the 4 missions, and 2.5k every discovery made, so if you get all the discoveries first try, you'd make.... 34 platinum by running all 4 missions twice. A nice bonus to help you get started
Don't buy from the online store, look around Amazon.com and such, a friend of mine got EoTN for something like 20 bucks there.
Prophecies Platinum edition comes with Prophecies and EoTN.
Personally, I'd suggest getting them all at the same time, due to how easy it makes things. (At level 12 if you start in NF you can go to EoTN and get max armor, or take a ferry to max armor at level 2 for ~500g)
Also, as for what character to make... you can change your attributes, skills, and secondary prof. in town anytime you want once you're ascended, which is roughly 2/3 the way through prophecies, or 1/4 the way through factions/NF
Another reason why I'd suggest NF to be honest... you get PvE-only skills at level ~4, max armor at level ~3 (if you have 5.5k plus materials) you can get your 30 attribute points at level ~6 (In factions you need to be level ~15 and past when you'd get to level 20 in prophecies)
Plus doing quests there get you better free stuff, and heroes... But I ramble :P (I really like how easy it is to start there)
Overall, you have 4 character slots starting, and +2 for any campaign you get, so you'll be able to have 8 characters when you have everything. Enough to make one of every (but two) So you'll have plenty of time to make anything you'd like. Personally, I started out as a ranger, and hated it. Then I made a necro, and loved it. Later on, I made a ranger again, and loved it. ^^; As a starter class, I'd suggest a necro, elementalist, paragon, or ritualist.