How important is crafting?

[Niwashi]

a) How important is crafting for those who are not going to be investing billions of gil or spending all day macro-crafting?

b) Can we get by without it?

You are certainly going to want crafted goods at times. Whether that means crafting them yourself or buying them from other crafters is entirely up to you. Many players don't get into crafting at all and simply buy all their gear.

I get the feeling dungeon loot is superior to crafted goods at the moment.

The better dungeon drops are superior once you get them, but in the meantime, you're still going to need gear to wear. While leveling, it's likely that at least your first class will outlevel the good dungeon drops before accumulating a full set, so even at levels that have dungeon drops, you'll still need to start with crafted gear until RNG works in your favor and you get the loot drops. Also, there are somewhat large gaps between good dungeon dropped sets, and for those intervening levels, the best gear in game is crafted.

I've seen talk of materia melding, but is that something that is important at any point outside of crafting? Do you need to craft to materia meld?

You have to craft to be able to meld materia yourself, but anyone can create materia, even if they don't craft, and so long as you have both the materia and some gear you want it added to, you can ask another crafter to do actually meld them together for you. (It's considered polite to tip them for doing so, but since it only takes a moment and they don't need to provide the materials, that's typically a fairly minor cost.)

d) Disregarding gear itself, what else does crafting bring to the table?

Consumables, particularly the food that Culinarians make, is another big one. There's also an assortment of stuff for decorating houses, and a few other miscellaneous items, but gear and food are the main categories.

e) Is it viable for players to just pick up one or two things and casually progress through them? Say for example, I'm a strange type of guy who doesn't mind fishing as a 'break' from defying the laws of physics and making big numbers pop up. Would it be sustainable for me to buy equipment and whatnot to progress in fishing without gimping myself or destroying the bank balance?

That's certainly viable. You'd need to buy gear and fishing tackle, but could then sell fish, so can come out ahead overall. (You'd likely want to learn enough about Culinarian recipes to know which fish are useful.)

Say, I decide to add a crafting class to that, let's say I go for Culinary because it seems to tie into fishing. Can I casually fry eggs and make chicken nuggets all day long without so much as being murdered financially due to gear requirements or reliance on other crafting classes?

Culinarian is one of the more self-sufficient of them in not needing many materials made by other crafting classes (well, some items from Alchemist, but only on a few recipes). It's dependent on two of the gathering classes, though: Botanist and Fisherman, so I'd recommend trying both of those if you plan to be a cook. You'd spend a lot on all the Botanist-gathered ingredients if the only DoL you're pursuing is Fisherman.

It varies by which class you're interested in, though, as some of them have more dependencies than others. If you were interested in something like Weaver, for instance, you'd find it requires a fair amount of leather, so is expensive to level without also leveling Leatherworker. I recommend anyone interested in either of those to level them together.