I'm a sophomore here at BU, ran cross country and track throughout high school and ran my first marathon about 6 months ago (the Bay State). I never trained with gels or anything like that (just a bottle of water that I'd refill every chance I had), so I figured that I'd approach the marathon the same way, that I'd just rely on the water or Gatorade provided every couple of miles to keep me going. I had to cut my training a bit short to hold my shin splints in check, so the longest runs I did going into it were only about 15 miles and at race day found out that I needed something a bit more substantial to keep going - there was one water table that also had gels about 16 miles or so in. Despite the bad reputation energy bars/gels have, that gel was the best thing I'd tasted in years because of the situation. Even if you don't think you'll need them, I strongly recommend bringing along a few gels. Make sure to use the bathroom before the race - no matter how long you have to wait in line, if you start the race with an empty bladder, you should have a pretty good shot at finishing without having to waste any time during the race stopping to relieve yourself. Be careful not to overdress - if it's about 55 or above, you will be fine with just the singlet and shorts. Even if temperatures are in the 30s, I wouldn't add much more than a long-sleeved shirt and maybe a light pair of gloves unless you're willing to toss the extra clothing at some point along the course or be uncomfortably hot. Finally, I recommend taking at least a few sips of water at each water stop whether you think you need it or not; there's no need to drink the whole cup or grab multiple cups early on, but once you start to really feel thirsty, it's much more difficult to effectively counter the dehydration during the race.