Hey there, I was in the process of thinking how to make a match 3 game as well. I think at it’s basics you need to create the grid first. Think of it like a chess game. You need to create the board first before you start doing anything.
You can do that by using a table array. Have a table array contain different positions and place your gems middle point at each of those positions. I think this will be how i did start going about doing it. After that ideas of how to randomize, switch and such will come to you more easily because Corona API will be able to help with that. (math.random, transition, etc)
Here is a link as well which you will be able to google for. Might spike a little idea to what you wanna do.
http://gmc.yoyogames.com/index.php?showtopic=494211 [import]uid: 39846 topic_id: 23999 reply_id: 96749[/import]