if you're going on a stripped down road bike then you're limited to what to take.i use a rack pack.
for clothing i just take a waterproof and sometimes a thin top.
for tools i take a alien multi tool and a couple of tyre levers as the tool has the chain splitter and spoke key on it.i take a spare folding tyre and two inner tubes, and a couple of cable ties.
for drinks i take a couple of bottles of water or blackcurrant cordial as i can't stand the energy drinks.
food wise i used to take mini mars bars and start eating them after about 40 or 50 minutes, probably every 30 minutes, now i take marmalade butties which get eaten somewhere around the 50 mile mark, any other food i need i can get from a shop i leave a mars bar in teh bag for any emergencies.. my son is building up to his first 100 in may and we're up to about 70 miles now, he takes an assortment of his favourite snacks in his rack pack, far more than he needs but it's there for emergencies.
money wise it's whatever i have left!
if you have someone with a car who can collect you then you could leave out the tyre, but we don't so it's there to get us home.
if you can then i would advise getting some longer rides in, if you commute every day then it should give you a good fitness level but you may struggle over the distance ,especially if you ride it at someone elses pace.
my son started riding in januray mainly to ride our clubs 50 mile ride , he did that off a few 30 mile rides and 3 50's.he then decided he wanted the grand slam which is a 100, 150 and 200 so he now rides a 40-50 mile and a longer ride at a steadier pace ,this weekend it will be a hilly 70, next weekend possibly an 80, but he's got enough time to build to the 100 in may and then continue to build up his mileage and speed for the 2 longer rides.
i've been riding 100's for years and know what it feels like when your legs fall off at 80 miles! so feel preparation is the key to an enjoyable ride.
good luck!