For a half marafun, I don't bother with gels, just take whatever sports drink or water is going at the aid stations. Might have a small energy bar before the start if I feel peckish.
For a full marafun, I carry two non-caffeine gels on the right of my race belt and one with caffeine on the left to give me a boost at around 30km. I take the first one about an hour into the run and the second one 30-45 mins later. If there are bananas or stuff at the aid stations I sometimes skip one of the gels. I used to have just a slice or two of toast for breakfast but nowadays I have a bit more breakfast, helps keep my pace in check for the first half hour or so