>Aquaman goes: Brightest Day, then onward into his current solo title from there?
Yeah, pretty much. Collected volumes of the first Aquaman series are handy too, though not strictly necessary. The important things to know from the early stuff - other than basic origin shit (which they constantly bring back up anyway) - is that Mera comes from another dimension and that Black Manta killed the baby that Aquaman and Mera had together, but I'm pretty sure you get a quick review of all that between Brightest Day and current issues anyway.
>I guess the main thing that seems daunting is just knowing what the fuck to buy. It seems like neat-and-tidy maxi-series are outnumbered by convoluted cross-over arcs that incorporate not just the maxi-series but a number of tie-in mini-series and storylines in other titles. It just seems like a fucking mess
Yes, this, a thousand times over. It's pretty clear that it's all a shameless sales tactic to get you to buy every single comic on the shelf, despite whatever intention you may have to buy a single title pertaining to a single character. My opinion is that, the way they do things at the moment, they might as well just release one volume a month, 52 times thicker than a regular comic, titled "DC Comic". It's a solid tactic that works well for them once a person actually starts to buy comics, but I think the heavy-handedness of it costs them a good deal of potential customers who decide they'd rather not get wrapped up in all that nonsense.
If it were up to me, I'd give each of the JLA core team a comic (Superman, Batman, Aquaman, Flash, Arrow, Wonder Woman, Lantern). I'd use the Type-Comics as a venue for those character's "Family" teams, with no set central character (Detective Comics for the Bat-Fam, Action for the Super-Fam, etc.) - maybe as a double-size issue used for inter-family crossovers, and double features where the back-up trends toward spotlighting lesser known characters in order to generate interest in them. For characters that have a HUGE family of associated characters (Again, Bat-Fam and Super-Fam), I'd probably broaden the number further with a girl-characters and a guy-characters comic - like Dark Knights and Birds of Prey would be the Gotham stuff, rather than giving separate titles to Batgirl, Batwoman, Nightwing, Azrael, Robin, and any number of other Bat-titles that come and go all the time. I'd make a couple titles specifically for cross-over stories between two or three characters (Worlds Finest and Brave And The Bold come to mind), rather than using their main titles for such things. Then there'd be the team comics, like JLA and Teen Titans, which is the ONLY place I'd let an major event cross into, with the exception of events that crossover into titles with stand-alone stories rather than a single tale chained together throughout them all. After that, there's just some miscellaneous peripheral characters that are "big", but don't have an associated family of characters (worth mentioning) that come with them, like Hawkman, The Atom, Firestorm, Swamp Thing, and the like.
Basically, the whole thing could do with some streamlining and simplification, in my opinion. There's fat that needs to be trimmed, and Type-Comics that need act as a showcase of that type, rather than just another venue for the main character that's now typically associated with it, and crossovers that need to be more restricted so as not lose a reader just because they don't have the money to keep up with it all. I certainly don't think they need a whole 52 titles going all the time, and the rate at which they change some of them out just proves it to me.