Here's just a quick tip for carrying gels while running longer distances. I only carry them for marathons, and I kind of hate the feeling of those waist bands. Turns out, you can carry them safely without buying anything.
All you need are your regular safety pins – you know, those things they hand out at every race for attaching your bib to your shirt. Take a gel, put it inside your shorts on the left or right side, and flip the top over your waist band. Attach the top to your shorts using a safety pin and it won't go anywhere during your race.
When you need it, just tuck it from your waistband - it'll let go easily - but be aware that the pin might open, so don't get stung. I found this works great and the gels don't bounce up and down while running. I carry three gels at most, so I don't know whether this works for more gels.