I just bought the base game and I want to more

Do i need to bought multiple packs of the new characters?

I just bought the base game and I want to more

Do i need to bought multiple packs of the new characters?

Short answer: no.

Long answer: If you only want to play campaign, no. If you want to play skirmish you might want more than one of the rebel troopers or rebel saboteurs.

Ally packs give EXTRA goodies, but you don't have to have them.

To ecco what has been said if you have picked it up primarily for the Campaign then you don't need to buy anything else just yet, although replacing the tokens with figures adds in some extra goodies that even if its just for Campaign Play I think is worth it.

If you plan to play Skirmish in a passably serious way, by this I mean more than once or twice in the basement with mates. Than I think that multiple Rebel Troops and Rebel Saboteurs are well worth it as the Rebels can have a bit of a scattered feel in skirmish without them IMHO.

The only other thing I am actually seriously considering just buying a second set of is Twin Shadows as I think the extra Heavy Stormtroopers and Sand People could be handy (more the deployment cards for the Troopers) and I plan on some head Swaps for my Imperial Officers so having multiple Rebel Heroes is not a big thing for me as I am happy to convert.

The only reason to get an extra core set is to have more Imperial Officers, which with the way the new pass activation works I am not sure is really needed anymore (if it was "needed" or not before is a different discussion...) and to get more Royal Guard which are a solid unit which can find there way in to multiple Imperial lists.

Hope that helps, and welcome to IA.

Kris

...The only reason to get an extra corset...

I myself own two corsets and a couple of twin shadows, plus repeats of rebel troopers and sabs; not because I play competitively but because I'm only into skirmish and want my family to have the widest palette to draw from so we can have decent themed squads and so forth. Plus, I'm a sucker.

If you are interested in campaign right now, don't buy anything else until you've played a few skirmishes and decided if it's for you.

To add to what everyone else has said, each pack includes as many copies as you're allowed to use at a time of all of its components, except of course for the unit itself. (For example, if you're allowed to use two copies of a command card, the pack it comes in will include two copies of it.) So for unique characters, there's never a reason to buy multiples; for generics (i.e. the Rebel Troopers, Rebel Saboteurs, and all of the upcoming third and fourth waves), you buy as many as you want to be able to field.