Can I group text on iPhone without using data?

Sadly I have a small data plan, because for a family of four, lots of GBs is just way too expensive. So being the college student I'm, generally sapping all of our data, I'm trying to cut back on use. One thing I noticed is my Messages was using a lot, but is that because I had iMessage setting turned on? I read that its because I have this enabled is why it uses data. Now that its off, will my group messages just apply to texting rates?

No, as there's no support for group conversations via the standard SMS.