If you just want to get started playing casual 100 pt games with your pals, this is what I'd suggest for starters:

Core Set

Firespray

TIE Interceptor OR TIE Defender

Millenium Falcon

B-Wing

This will give you set of small fighters and a couple awesome big ships for Rebel vs. Imperial dogfights. Without going into detail, this would also give you a great set of upgrade cards that will be useful if you will eventually want to play more competitively.

I don't think you need 2 core sets to start out with. The money is better spent on a fun large base ship.

Welcome to the game and forums! I won't give any you advice. My addiction to this game started in February of this year and I went nuts. 3 cores, multiple purchaes of everything except the Tantive and acrylic templates. I haven't decided on a faction so I fly to have fun. I doubt that my abilities are tournament worthy but I've met some great people and learned a lot. One thing I did learn was not to look at your bank account. It'll just depress you.

Whichever way you decide to go, have fun and welcome again.

I only started playing X-Wing this year myself, around May.

Some good advice has already been given so I won't suggest any ships but if you get addicted to it like most of us have, you'll end up with at least 1 of eveey ship lol!

In two and a half months all I'm missing is the Tantive/Raider from all 3 armies.

My wallet hates me.

It's getting a lot tougher to see the value in two cores off the bat unless you're providing for more than yourself or really want to go with a TIE swarm. There's so many ships to choose from, and there are two expansions for the X-wing already that you'll eventually want anyway and soon the same will be true for TIEs. I purchased two cores in wave 3 and I could easily have done without it, so I'm with Stone37 on this one.

2 core sets or not, well it depends.

If you want to just get a collection for only your self to play and have a robust x-wing community with a weekly schedule that always provides players then sure 1 is all you will ever need, unless you want spare components.

However say if you want to play with a friend or relative who may not have their own collection sure that you could use the learning missions and share everything but in order to play a proper game using only your collection between two players then 2 core sets is a must.

As for me well I started earlier so having 2 core sets were ideal because I get extra components and can play with other folks that don't have their own collection. However I never got the full 8 TIE fighters for the swarm but I will get one with 2 core sets 2 TIE Fighter expansion and the newly announced epic ship will have another 2 TIES so I would get a perfect 8 TIE Fighters once the Carrier is released.