They're all so pretty! Four at once! You ARE going to be busy LOL
Yeah, You're definitely going to need more stuff.ummm First of all how big is the cage? They should have a few more perches-different textures and sizes-like natural wood, rope,or maybe cement perch.They need dif textures/diameters to keep their feet healthy. Not sure about how many food/water dishes you need but definitely more than 1 of each,a cuttlebone,and a few toys/swing(s).
I only have 1 so others with multiple birds will have a better idea of how many of each thing you should have.
The fun part will be trying to put things in the cage if they're still really skittish.I think I would put just 1 or 2 things at a time and move slowly and talk nice while you're doing it, then let them get used to the new items for a while. Maybe I'm wrong but it seems like too much too fast would freak them out.
I'm sure others will have more ideas to offer and maybe even links or suggestions where to find the best deals

It was sooo nice of you to take them in and give them a good home.And great that you are looking into what they need to be happy and healthy. 2 thumbs up to you!