My crafters are 63 to 65 with gold at 68. Trying to get them all to 70 and then hopefully learn how to make some gil with them because I have no idea what's efficient.
And then the common items that most lvl 70s can make regardless but that still sell because of the convenience of not having to make them or non crafters buying them to get stuff crafted. That's your basic ingots, leather, cloth and also common consumables like potions and food for raiding. These move extremely fast, but the margins are low so you need to craft a lot to see any result. You can make crazy amounts of money when some of these go low for whatever reason, and they're very nice to make afk and often require very little gear to make, so imo they're a good way to get started(but don't flood only one item, have to diversify a bunch).
Past that, you have plenty of more niche markets that will make a profit but depending on the demand it might take a while. Stuff like crafting crafting/gathering gear(the early stuff from 4.1 and what not to help bridge the gap and also leveling gear for lower level character), older cosmetics big ticket items that aren't worth nearly as much now but neither are the mats, and housing items.
If you want to make money crafting, you'll probably have to spend a fair amount of time scouring the AH, checking how often things sell, how many there is for sale and how much they cost to make(to see what kind of money you make per item). It's quite a time investment to find niche markets for stuff but once in a while you can make good money with them. It's not as easy with scrip gear though since one of the big vanilla money makers was making crafting/gathering entry lvl gear since everyone had to get that to even get started doing anything else, but now you can get scrips via weeklies and stuff and get your basic gear on much more easily.
But regardless pretty much everything you make will sell for more than the sum of the materials. Only exception is when the materials fluctuate in price before you sell the item, for example right after a new patch if you buy a bunch of overpriced new materials that were just added, craft the item but don't manage to sell it within 3-5days, there's a good chance you'll be losing money or barely breaking even. So mostly the trick is finding what makes the most money, but regardless your money goes up.