I've got some credit left in my steam account and was looking to buy FFIV with it, but I don't have enough for the expansion pack. Now longterm I'll of course have to fix that, but for the next couple of months I can get away with it.

So I'm wondering what do I miss out on by not buying Heavensward immediately. Am I still eligible for 30 days free if I use the free trial?

I've seen these questions asked before, but they're all a year old now. So I figured it was worthwhile asking again.