So my "low" account is my fairly new one and the one at which I am forcing myself to play economically smart from the beginning. Today I'll cover what characters I am planning to have and what professions I have assigned to them. My plan is to have 5 chars down the road, with 10 of the profession present. I want to have as much synergy as possible (e.g. having the crafting professions which need level 84 to gain access to Twi.Hi. patterns on as few chars as possible).
My first character is a Druid. Due to flight and aquatic form, this is the superior farm class. Currently I have 360ish Herbalism and 300 Enchanting (so there's my first mistake). I plan on dropping Enchanting for Mining as soon as possible. Though disenchanting and reselling has been one of my two major money makers on this server, the cost to relevel it on another character shouldn't be too high. My Druid is four levels away from Flight Form and once he gains that, I want to use that to bring Mining to 300 before heading to the Outlands. Ultimately he doesn't need to hit max level that badly, since I could start gathering in the Cataclysm regions with level 75.
The second character is a Paladin. He sports 300 Alchemy and 300 Inscription. My reasoning was having all herb processing jobs on one character. Since he's a Dwarf (Archeology racial) and already 40-50 days into Minor Inscription research, there isn't much to be changed here. He's only five levels away from being able to level to 375, so that will be my highest priority, since Glyphs are my second money maker and opening up the market for processing TBC herbs will increase the potential profits for him. Also, Primal Might transmutes are waiting. So hitting level 75 sooner or later would be a good idea both for MFC shenanigans and all sorts of transmutes.
It gets kinda blurry after those two. The professions I haven't covered are Skinning, Tailoring, Leatherworking, Jewelcrafting, Blacksmithing and ultimately Enchanting again. I am left with three chars. One of them will be a newly created Worgen Deathknight, who'll take care of Tailoring and Skinning. AoE farming of both cloth and leather should never be passed up on (and my Paladin is fairly set in his stuff) and the racial will make the latter more efficient.
This leaves two characters, a Warrior and a Hunter, both around level twenty right now. At this point, I am unsure how to split the remaining four professions. Jewelcrafting and Enchanting have nice synergy when doing the Saronite or Obsidium shuffle. With Leatherworking and Blacksmithing on a single character, two of the Twi.Hi.-dependant professions would be on one character. Does JC/Enchanting on the Hunter and the other two on the Warrior sound like a good idea?
You'll notice I left Engineering out of the equation until now and I'll continue to do so. While being a fun and useful profession, it doesn't offer as much as the rest with regards to making money imo. And being honest, bringing 5 characters to level 75+ and 10 professions to the useful maximum will be a lot of work already. Maybe if they bring in epic gem transmutes with a CD timer, leveling a 6th character will be justifiable.