I'm glad other people struggle to get it right too! I reckon this might just be a case of trial and error for a while. Having everyone I talk to telling me to "eat before you're hungry" doesn't really help matters.
Taking advice from others about what / when / how much to eat is pretty much pointless except in very general terms ie, eat something at some point before you ride. My better half raced a 100 mile TT yesterday but has to fuel up no less than 4 hours before the start, nothing after that, yet many competitors are eating 2 hours before or less. She has a bowl of porridge with honey and a ripe banana and some rye bread often with peanut butter on. Sounds a lot but they are small quantities eaten very slowly [important]. During the race she has 3 gels [about normal for her] and several 500 ml bottles of water, I think 5 yesterday as it was very hot.
I would not recommend gels unless you are know what you are about, and even then different makes have very different effects, but you do need to take them with plenty of water, otherwise expect to feel sick if you are working hard.
Fitness also plays a huge part in eating and drinking as the fitter you are, the more efficient your body becomes and the less fuel you need at any given speed.
Sorry if that was a bit long winded but basically you need to experiment a bit until the right balance is found for you.
( ave 14.7mph/23.6kph)
