Get 2 equal T-shirts. One to cut out several strips and the other one to later pin the ruffles.
For the strips I cut the shirt vertically and measure depends on how you like the ruffles, big or small.... width or narrow, depends on your preferences.

With sewing machine, sew a straight line on top of strip with the loose set in your machine, then pull one string to make the ruffle. Again, your choice if more tight ruffle or more loose.

I used all the cut out shirt for ruffles!! in some cases had to use 2 stripes overlapping to make it from one side to the other. I started pining out to the t-shirt. And then attach with sewing machine to the T-shirt.

I started pinning from the top to the bottom, that makes a kind of U form cause of the neck, then going down I tried to get them more straight horizontally. This was the most difficult part for me!!!
I try it on occasionally to see if I was pleased with results, before continue applying more ruffles down.

Ready to wear!! I normally hang my creations like this so I can look at them for a couple of days.... then if I really like it I wear it!! just a little annoying process I have!!

Voilá!!! I really love how it turn out!!, think I´ll make another one for the summer, sleeveless!!

Ciao!!