No matter what, you should always seek to keep at least 5-7 million credits in the bank since that's enough to get a toon to lvl 70 gear 8, which I think is enough to make it viable for events like this. If that's enough for you, then be patient or drop money for crystals. That's how this game is designed.
As for this event, there's been hints for weeks about it happening. You should have been side farming at least one scoundrel after you hit the level cap and now you've got a week to focus on another. Everybody has Chewie and Nute, Greedo, and Cad are easy to get and none of them have to be perfect. This whole "woe is me I don't have 5 seven star maxed out arena ready scoundrels so this event is worthless" attitude is unfounded. Start off with 2 good ones and three okay ones and you'll probably do fine.