Sewing with stretch materials (t shirts, track suiting) is super easy as it doesn't fray and you don't have to finish off the seams. If you have an over locker then it's even easier. I made heaps of t shirts, grow suits, track pants and jumpers for my kids when they were little. That type of fabric is cheap and really easy to wash. If you are in Australia then Spotlight stores sell a huge range so it's easy to buy a bit and experiment.