Even before being diagnosed I was used to carrying at least a single water bottle and few gels for regular runs and more for longer runs (over 2-3 hours). Now, for every run over 60 minutes I carry the same things and just adjust quantities.
I use a Camelbak pack (don't remember which one, I've had it for years) - it has a reservoir pocket that holds the big water sleeve (I only use this on longer runs), 2 pockets that hold my assorted "stuff", and a side pocket on each side that each hold a 24oz water bottle comfortably.
On normal length runs I'll carry 1 bottle of water and the other of an electrolyte drink (specifically Succeed Amino), one 12-pack of glucose tabs just in case, and about 1 Hammer Gel pack for every 15 minutes that I plan to be out (I only use 1 every 20-30 minutes, but this means I have extra just-in-case). Since all of my carbs come from slower-digesting carbs, I don't really have much in spikes or serious lows as long as I stay on schedule.
For longer runs, or runs where I know I'm going to have limited access for any sort of refills, I'll take 2 bottles of Amino and fill my camelbak to the max for my water. I also bring at least 1 extra package of Amino with me to mix on the go if I want more.
The great thing about the Camelbak is that while it's not hard to carry, it gives me easy access to just about everything - the pockets provide space for my phone, wallet, camera, meter, strips, etc. without difficulty and enough room to spare for a fleece vest or light jacket or something too, which I often bring along. It only cost me about $50, and was probably the best money I ever spent on running gear besides my FiveFingers.
I will switch from MDI to an Animas Ping the end of this month, and when that happens I am adding a SPIBelt to carry my pump in and will have an extra pocket or two to keep other stuff close by as well.
Obviously, YMMV, but this has worked very well for me for unsupported runs with no available resources but water of up to 30 miles, and supported runs even longer than that. If you have any questions that I can help with, definitely let me know either here or via "conversation"