Why not search in the app store for "lds dating" ? You can tell if the app is free by check if there is the text "In-App Purchases" besides the app name. Well this is actually how I did it. And my comments below for your reference:
LDSmate: Free. new but I enjoy all the fun features it offers. And there are new members joining every day. it seems promising and more fun than the others.
Mutual: Free. simple swipe left and right. I personally just a little sick of that. No other fun features.
SaintSwipe: Free. nothing special but again swipe left and right.