I have been playing several characters for some time. I like to try different professions and find what I like. I don't care about minmaxing, but I like to earn some gold.
I started with Herbalism and Alchemy, which I think is both easy and profitable, I could earn something even with low-level potions. Selling herbs is profitable in itself.
On another character, I wanted to take Mining for certain and was thinking about Jewelcrafting or Blacksmithing as a second. Mining has definitely paid off, farming thorium or mithril is very profitable and brings in tonnes of gold. For my second profession, I chose JC because I heard about transmutation in Alchemy and it seemed like a good synergy, because I can cut gems. JC is a fun profession, of course it's not as easy to level up as Alchemy, but I've reached level 300 and haven't gotten any gold from it yet.
On another character, I took Tailoring and Enchanting because I heard that it's a self-sufficient choice, and they synergise well. I haven't levelled them far yet, but I've definitely read that Tailoring brings some gold from bags.
For the last character, I definitely decided to take Inscription because I like the theme of the profession and the whole design of it.
After reading some posts on Warmane Reddit and some dusty threads on this forum, and hearing the opinion that Enchanting and Inscription are not in demand at all. That if the price of glyphs is about 30 gold (as it is now), then it is almost impossible to sell. I've read that Blacksmithing and Leatherworking have no way to make money except for the final crafts.
So I come to the conclusion that all gathering professions bring in a large amount of money, but are not very interesting in themselves. Alchemy and Tailoring are also always in demand.
MOST IMPORTANT
Is there any point in leveling other crafting professions if I want to get at least some gold from them WHILE leveling them? I would also like to ask for clarification on the status of Inscription and Enchanting. Does Inscription bring enough gold now and is Enchanting useful except for very high levels?
My experience this is what I can say after maxing every profession on my toons.
Depending on the expansion, some professions are more useful for your character(s), and some are more useful for gold farming. Gold as well, especially @ lvl 80, is quite easy to come by itself. It's very easy for me to get 5k in 3 hours selling mats + dailies alone as each daily in Northrend is 50g a pop and being a miner, selling Saronite at 60g a stack currently which I get very quickly. Even Copper sells @ 50g a stack right now. You can farm 25 stacks in an hour with a good route! Starting out brand new, skinning is the best as you can vendor or even sell the skins to boost your economy for skills (Since you level really fast, it's a must imo if you're fresh).
In the end you need to ask yourself: Am I really in this just for the gold? (What's a goal with gold? The mammoth mount? High ilvl purps for my alts? Flying for my alts?), or do I need 34 strength/resil gems Jewelcrafting, or do I need 2 more bonus sockets from Blacksmithing, or 340 Haste for 12 seconds on demand from engineering (All UHDK relevant as an example). Sometimes the answer is yes, this character needs gold, sometimes it's no, I need these for PvE/PvP/Guildies.
Personally, gold comes in large amounts over time on WotLK. I'm in no rush to get that sweet mammoth mount again on my mage, but if I keep doing dailies, I can get it in 1-2 weeks tops if that's something I want to save for.
EDIT: Sorry! I didn't answer your most important question! In my opinion, there's a lot of glyphs on the market as is and someone always has a toon for it. They can sell fast if you undercut, but if your aim is gold, I'd say Inscription is not the best way to go. Enchanting is useful as well but I've seen it come down to a bartering system. Sometimes people pay me 200g a pop for a good glove/head enchant, some offer 50g and I take it too. I don't get too many requests so I honestly just enchant for guildies. Enchanting back in retail 3.3.5a in my opinion was more useful then and more lucrative money wise, than it is in Icecrown on warmane. I'm not sure if it's because of the x7 rate but that's just what I see personally.