In making these jammies for Tee, I chose to use Simplicity's pattern number 4767. I was really pleased with how it turned out. I made a few alterations to make it very simple that ANYONE could make these. The first is that I used the short sleeves and used the hem as a casing for the elastic, instead of hemming and creating another casing. I left off the ruffle at the bottom. One thing to note is that you might want to go a size or two too big due to the chest fitting pretty snug. Not tight but snug enough that it is hard to get in and out of.
Give them a try. They are easy and Tee loves them!