I have put off buying proper cycling equipment for years, because I didn't want to become Golfclub Man. This is the rich individual - God knows how I arrived at his gender - who buys a load of expensive stuff before he can actually do anything with it, and is forever mocked and shunned by his golf associates. This dogged behaviour (of mine, not Golfclub Man's) has led me to really, really appreciate bike equipment, because I know well what it was like not to have.
Don't buy a tiny pump to take everywhere - when you do get a puncture you'll be in a town, because that's where idiots break beer bottles in gutters, and unless it's the middle of the night you'll dip into a bike shop and borrow their standing one, because they are so brilliant.
Do buy a standing pump - they are brilliant. Oh, and do buy spare inner tubes as well as cycle repair kits. Repairing holes is a task for January, when you aren't drinking and all your friends are ... I don't know, dead, and you have already run up some curtains and rearranged all your furniture. When you actually want to ride your bike but you have a puncture, you want a spare inner tube.
Do buy those little levers for unhooking your tyres. They are much better than spoons. Don't buy those canisters of gas that instantly inflate your tyres, and I'll tell you for why - you wouldn't want to rely on them in an emergency/triathlon scenario, because you can't fully work out how to use them. But then, if it's not an emergency, why waste them when you could just use your standing pump? (Don't tell my boyfriend: I got them in my Christmas stocking.)
Do buy a proper jacket. You simply will not know any pleasure in inclement cycling until you do. Oh, to be toasty and visible! It's every winter cyclist's dream! Do buy proper lights - you want your bike to look so like a disco that 15-year-olds stop to snog on it.
I am going to be controversial here and say don't bother with a really good lock. Sure, don't have some ridiculous 5mm loop arrangement, but those really industrial ones that add 20 pounds in weight to a bike that was only so expensive in the first place because it was light - it's just pointless. I've had bikes nicked with the most hardcore Kryptonite locks, and I've still got the bike whose lock isn't even recognised by my insurance. Don't tell my insurance.
Do buy some padded pants, or at least do if you have a razor-seat. I thought these were for jessies; then my sister's boyfriend told me that razor-seats were designed to be used in conjunction with the padded pant and, by God, it's changed my life. I still don't wear the full gear, though, unless I'm on an epic cycle - I just wear the pants under my regular clothes, and get overtaken regularly by people who very clearly are in the proper gear. They sometimes give me a sly look, like, "Why spend that much on a bike when you're just going to pootle along in ridiculous clothes?" And I simply smile to myself and think, "Ah, friend, I'm not in a hurry - and I'm in PADDED PANTS!"
Do also buy cycling gloves, and cycling inner gloves, if you intend to do proper journeys. I wore my regular leather gloves with their woollen innards on a bike ride recently and gave myself right sore knuckles - and a number of people asked me afterwards if I was the missing link. Though that could have been because of my neck hair.
... and cleats gave me more muscle
It has taken me ages to get around to cleats, mainly because of what other cyclists say about them. Basically, your shoes click into your pedals - like toe clips only more efficient - which means you can get power from your leg's upward move as well as its down. In other words, it's like having twice as many muscles. There's really nothing to be said against it ... apart from that, when you ride with them you forget at traffic lights, panic, can't get your foot out and then fall off your bike - if you're super-unlucky, right underneath a moving car.
Now it is true this can happen, but it's also true that it never actually has happened to the person spinning this scary rumour. Often they have never fallen off, they've just nearly done so; or if they did, it was only towards the kerb and they didn't hit anything. Or maybe a plastic bag.
Why do they overstate it so? I suppose it's like childbirth: they would hate for you to think it wasn't really hard, just in case you failed to appreciate them properly. It's really not that hard. Though you probably will fall off once or twice ...