So I'm starting to get into Armada, Just got my core set and some Rebel ships, Looking for some Imperial ones to have a balanced playing field. I'm not too concerned with competitive play just for some ships to have enough for decent sized battles with a relatively even playing field. I have the ships that came with the core set and an Assault frigate and a MC30c and only a single Victory class. Any suggestions for some Imperial ships to even out the battlefield would be great!

ISD and GSD

Above suggestion is good.

Picking up one of each small base and flotilla pack for each faction, and squad packs 1 and 2 for each faction, will give you enough options to play dozens of lists. Only large ship you absolutely need IMO is the ISD as it is the cornerstone of most imperial lists.

http://cannotgetyourshipout.blogspot.com/2017/03/building-imperial-fleet-on-cheap-250.html

Given you've already got the core set, you'd only need to pick up the additional items that you don't already have. It would be up to you if you wanted the more combat-centric initial version or the squadron-heavier second option.

ISD, Arquitens. You get a very Imperial looking fleet.

Wait on the GSD.

If you don't have an imperial Star Destroyer, buy one!
Great ship!