Ideas for tetris like game behavior

What would be the best way to make actors and have them move downward continously. I thought about using gravity but it seems to take a lot of memory. Also I would love to have them fall in a tile like movement.

I was thinking every X seconds have the actors move but I dont know whats more taxing on game performance an always event or time event?

You probably want to go time-based. Check this out:

http://photongamedev.wordpress.com/2013/06/03/the-do-after-dilemma-building-your-own-time-tracking-mechanic/

Second, I would actually recommend "constructing" pieces out of individual blocks. For instance, in tetris, each block has four individual squares. You would simply move four blocks in tandem with each other per the formation, in that example.

Finally, for performance sake, I would recommend going with lagless actors:

http://www.stencyl.com/help/viewArticle/163

perfect thanks and I am in talks of tuo about that as well!

I plan on having a good amount of content in my game and I just want to make sure its working good from the get go and it remain a flash game!