When I am at Target...... for let's say ziplock bags, I have a tendency to pick up an extra clothing item or two. In particular, I like to stock up on these Mossimo v-neck tees. They come in a variety of colors, are perfect for layering, working out in or even dressing up a bit.
I had some leftover fabric from when I had my wedding dress made, so I found a pretty cluster of flowers, cut out around them and sewed them directly onto my t-shirt. In about thirty minutes, I had a custom t-shirt for very little time and money.