One thing keeping some people from cycling on a regular basis is the notion of how much gear it takes to really "be" a cyclist. If one ever ventures into a bicycle shop, it can quickly become overwhelming. In addition to the bike itself (a pretty complicated area, if we are honest), there are all sorts of other oddments, clothing, lighting, racks, packs, and whatnot. Then there are the subtle and not-so-subtle pressures to "gear up" with as much of everything as possible, or to get tricked out with expensive speciality clothes.
Perhaps most off-putting of all is the notion, conveyed by all sorts of magazines, videos, still shots, and the "culture" of many bike shops, that cycling is essentially a form of sport for the wealthy and leisured, focused mostly on fitness, youth, or at least the nervous preservation of youth. All of this means having a lot of gear.
Cycling, like most things, has quite a few meanings and uses, sport being just one of them. For me, cycling is about transportation, connection with the community I live in, somewhat about keeping active, and mostly enjoying a slower pace of life. Gear is just a means to that end.
Because I live where it rains a lot, I have had to plan accordingly. I purchased a breathable rain coat in an eye-catching yellow, that makes me look like an overstuffed Big Bird, but makes me a bit more visible to distracted drivers, also. I found some rain pants that work well, though they aren't all that breathable (I found over the years that no matter what, you still get wet inside stuff like this, just from sweat, not rain).
I zip-tied my garage-door opener to the handlebars (this makes getting into the garage a lot easier, as there isn't an outside lock or handle on the main door), and then rubber-banded some plastic wrap over it to keep it dry inside. Classy.
I have some old cycling gloves that I use much of the year (my hands are prone to getting cold). A cycling helmet with an attached side-view mirror is another piece of gear I own. The biggest expense (outside the bike) I have incurred in getting my bike "kitted out" has been some good quality waterproof panniers. After reading online and talking with folks, I found that you get what you pay for here.
Then there are my "cycling shoes" (some tired rubber moccasins) for when it gets really wet--which is isn't all that often, really.
The kind gift of a bicycle pump has proven helpful, and I have some flashing lights for the front, the back, and spokes (in addition to the dynamo-driven ones that came with the bike), mostly with rechargeable batteries--these lights help with distracted drivers, too.
I splurged and got a cup-holder for the occasional mid-ride coffee and as part of a future umbrella carrier setup. A couple bungee cords prove useful occasionally.
That pretty well covers it.
Other than the panniers and the coat, everything but the bike was quite affordable or something I already had. It doesn't have to be hard, complicated, or expensive. I know one person who used old plastic laundry soap bins with handles as the basis for some very effective, rugged, and cool DIY panniers. He just added some bolt-on hooks to them, a few reflective stickers...and bingo: cargo-carrying capacity. Like many in in the daily cycling world, he just keeps his eyes on the prize of it all: affordable, effective transportation.