I have the core set plus the ISD and Home One.

I have played a handful of games and in every game the rebels went first and had an extra activation.

Using the just the core set I struggled to beat the VSD. However when playing with my friend he used the TIEs to attack ships rather than fighters and my Xwings made short work of the VSD.

Playing with all the ships my friend attempted same tactic and the Xwings pushed the game in my favour again, plus going first with Home One helped big time as she got the killer shot in before the ISD finished her.

So should if I continue to have more activations for rebels should I be giving Imperials first turn, as until I get more ships I can't match the rebels for activations.

Also what should I be adding to my collection next?

I'm also certainly adding Rebels and Imperial fighters I. I'm also thinking MC30 and Imperial Light cruiser as they both add something different to what I have.

MC-30, Imperial Light Cruiser and the fighter packs are all good choices for both factions, and the MC-30 and Light Cruiser have some great cards to add. Throw in some flotillas, maybe the MC-75 (when it releases) and Rebel Assault Frigate for rebels and the Gladiator SD and Chimera SD (when it releases) for Empire and you're well on your way.

As far as giving Imperials the first turn, it depends on what you prefer. Some people are all about that first activation, others aren't.

MC30s are definately fun though they favour having 1st player.

For rebels, I am always a fan of the Assault Frigate Mk II. It's a good all-around ship that isn't too expensive, and is surprisingly durable. MC30 is also a great ship that punches way above it's weight. I'd also pick up the Rebel Squadron pack to get some B-wings and A-wings

For Imperials I would also get a Gladiator if you want to get something for both sides. Dangerous ship with a lot of punch. You already mentioned the Imperial Light Cruiser, and I agree that its a fun ship to play with that is a little different than that ISD or VSD.

I recommend the MC-30c and Imperial Light cruisers as you mentioned. Both have great upgrades for both sides and provide each faction with a nice ship.

Also I recommend playing with objectives too. Don't just make one faction first, use the rules and play objectives for more fun.