How Do I Tile Over Wood Planks?

[Ryan Clevenger]

I'm currently remodeling the bathroom in my first investment property and I've hit a wall.  I ripped up the floor all the way to the planks.  They are tongue and grove but not actually pushed together.  They aren't perfectly level.  I went out and bought 1/4 in concrete board to put down before I tiled because thats what my mentor said to do.  But once I realized they aren't level I did some youtubing and I got some varying opinions.  Some said to put thinset down then the concrete board, some said to put plywood down before, and others said rip out the floor completely.  What should I do?  If I put thinset down do I need to put some kind of membrane down so it doesn't drip through the planks?  

Ps I'm trying to do as much by myself as possible