I would take a bicycle pump, a repair kit and maybe a spare inner tube. A light waterproof cagoule might be worth taking just in case the weather changes.

1)
Here’s what I take on my daily commute, 12 miles each way. It fits in a wide-mouth water bottle. Except for tire repair tools (2 flats), I haven’t needed any of these items so far this year.

Pump
Spare inner tube
Patch kit
Tire lever (Quick Stik, highly recommended)
Adjustable (AKA Crescent) wrench
Park Tool MT-1 Multi-Tool (it’s tiny with no moving parts, an alternative would be a simple hex key set plus small phillips and flathead screwdrivers)

2)
On a recent 85-mile trip I added:
Water
Bagels
Apples

I stopped at a couple of gas stations for Gatorade and candy bars along the way.

Oh, don’t forget money and a phone. If you’re really stuck you can always call a friend or cab.

@pezz knew i’d see a post up here from you sometime….

First thing to consider is what is your worst case scenario option for getting help getting home? You may only need a charged cell phone for a 30 mile ride. If you are determined to be fully self sufficient then I would at least carry a spare tube, patch kit, hand pump, a multi wrench for all sized nuts on the bike, duct tape, spoke wrench, pliers, crescent wrench, water and rations for your trek. Foul weather gear.

30 miles is not all that far and for the most part you should be able to rely on the more seasoned riders to help you out if you meet a big set back. Have fun.

Forget a pump, get a CO2 tire filler with a couple extra canisters. Small quick and easy. Make sure you get one with a rubber cover though, they get COLD

I usually make due with a multi-tool, tire lever, 2 extra inner tubes (just in case), a patch kit and usually have both rear (intermittent red) and front (high powered Halogen) lights fully charged and attached just in case.