Need help making a decent profit.

[Katlyna]

Everyone's advice has been spot on so far.

My Favorites of the advice:
1) Add Materia to Armor/Weapons you sell (V Control would be the most logical IMO)
2) Sell intermediate items like HQ High Mythrite Ingots, Leathers, cloths, etc
3) PF Advertise your crafting (I usually charge ~200-500k for HQ end synths) for items which normally go for 3-5 million.
During patch updates commissions can be around 1m, while during patch drop offs 100k can be reasonable as well.
4) Sell other items outside the most popular items, furniture, glues, foods, potions, things which are both picked up infrequently (and selling competition is low with large profit margins) and items consumed frequently with small profit margins.

Also make sure to spread your sales out among multiple options. So when one thing goes ill, you can simply drop price till you're out of the market.

[Alahra]

When dealing with a swarm of undercutters, my best advice is to be patient and don't engage with them. In my experience, rapid undercutters on high end items like these are trying to force you out of the market, but if you stay, they will typically stop, as after a certain point, they're not getting enough of a return on their investments. Be confident in your pricing, so long as your pricing is fair. Once the undercut war subsides, yours will be in a better position to sell at higher profit for you.

As others have mentioned, it also helps to spread yourself out—as you can, make one of each tool you can craft, and that way, if an undercut war happens on one of them, you can rely on the others for profit until that one stabilizes.

[LineageRazor]

Make the stuff that sells the fastest(no luck selling High Mythrite Cross-pein Hammers? try High Mythrite Ingots instead) and price it at the going rate.

This. Many crafters like to make their own equipment, but still need the materials that are supplied by other specialists. Essentially, if you make a High Mythrite Saw, only Carpenters will buy it. But if you make a High Mythrite Ingot, Carpenters, Goldsmiths, Alchemists, Leatherworkers, and Weavers ALL have recipes that need those ingots - and even though Blacksmiths and Armorers can make their own, they may prefer to buy materials to save time.

Additionally, (and you probably already knew this, but just to cover all bases) keep in mind that when it comes to equipment, NQ results are all-but worthless. Easily-crafted, lower-tier HQ gear is BETTER than NQ higher-tier gear, and much less expensive to make. If you craft a NQ piece of equipment, it will not sell fast, and it will likely sell for far less than the cost of the ingredients used to make it. Materials, on the other hand, both NQ and HQ results sell well, because most crafters don't NEED all of their ingredients to be HQ in order to craft successfully. For them, some, or even all ingredients can be NQ, and so they will happily buy your NQ ingot.

[Bourne_Endeavor]

Since we're on the same server, I'll give you my method. Look through low end gear and stuff you wouldn't necessarily think sells. I made 10 million off selling mostly leveling armor and furniture. You do need to be proactive to combat undercutting, but only engage with it to a reasonable extent. If I put something up for 70k and someone undercuts me by 20-30k, I'll generally wait on them because someone else will take their item first and now I'm back on top with my higher price. Basically, don't always look to the expensive items to sell. You can find a nice fortune through selling mats and low end stuff, especially if you have multiple retainers or alts, and thus, can put up a ton of stuff at once.

[Alisi]

Probably the best time to sell housing items would be right after an update that adds new housing ...

This is hit or miss. I've tried to get into it on my server but they don't sell like hotcakes, as you'd assume. You'll look at the prices of stuff with cheap materials and it seems good like easy money but the people (on my server, at least) are very good at driving away competition. I don't honestly think it sells that high. I think almost all the money I've made that way was because I was sick of getting instantly undercut and so undercut them all by a TON (and the people who were undercutting me would buy the stuff.) I don't think I ever sold any furniture to anyone other than the furniture tzars on my server. XD

My way for lazy money making is to do the maps, doing glamour triangles, finding the GC mats that'll turn a profit, or selling NQ components to things other than the current crafting tier (like the eikon ingots, etc. I don't bother with those. Generally crafters don't need them so the demand is less -- it's simply less expensive to make them yourself). I don't bother with HQ parts either (the nuggets and ingots) because the people who are buying them are the crafters who are just being lazy (like myself XD!) and can easily achieve HQ items with NQ mats so they won't pay the extra to get it in HQ. I know. It sounds strange but, in my experience, NQ sells better.

You won't hit the cash cow overnight but you'll be okay. You could also drastically undercut those people if you gathered/made almost everything yourself.

[MelficeAlmasy]

Gather camphorwood branches - craft camphor = profit.
Grade 4 carbonized matter is also selling fast, you can get 90 of them each eorzean hour

[Yeol]

If you cannot gather your own mats it means you'll spend gil and put the item for a high price on MB trying to make your gil back, while you'll see others offering the same item for cheaper price because they gathered their own mats.

I recommend levelling gatherer and unlock books. Each item is sold for about 3k-8k on my server and can help you make 300k gil daily.

[Nutz]

I find that 'big' items don't sell terribly well. The market is smaller and a lot of crafters will try to grab it up. It makes sense, after all you've worked to gear up and collect books/ gear to be able to craft these items. What actually tends to happen is people get to the point where they can make anything HQ and don't want to bother with the ingredients anymore, which every crafter needs.

Ingots, threads, cloth, lumber, and dilutions of several varieties are used to make more or less everything. Many people don't seem to want to make grade I 'X' dilutions and buy them from the MB, possibly because they haven't levelled ALC or because the ingredients are annoying. Similar things happen with all intermediate crafting materials, and as someone else already pointed out, NQ products are still worth money. Being a 3* crafter though, you can probably write a macro to regularly HQ most of the annoying 35 DUR recipes anyway.

These markets are also much harder to oversaturate because people need a lot of this stuff.

[Masekase_Hurricane]

This is hit or miss. I've tried to get into it on my server but they don't sell like hotcakes, as you'd assume. You'll look at the prices of stuff with cheap materials and it seems good like easy money but the people (on my server, at least) are very good at driving away competition. I don't honestly think it sells that high. I think almost all the money I've made that way was because I was sick of getting instantly undercut and so undercut them all by a TON (and the people who were undercutting me would buy the stuff.) I don't think I ever sold any furniture to anyone other than the furniture tzars on my server. XD

I never found it hit or miss and made around 20 mill last update on furniture. As I knew people needed Summoning Bell, Company Chest, Armoire, Moogle Letterbox and The Unending Journey.

Also the prices of most of these items had doubled on the first day of the update. I think the housing demolition timer restarts this update so in 45 days(need to add maintenance hours to this as the timer doesn't include these days) some of those items will be wanted again.

[Frowny]

I'll echo selling mats. People need em, they're not terribly hard to make and are steady.

I've dabbled in selling gear and hate it. I've already seen 2 people that love to undercut by 10k or even 100k for no reason. I've found people selling mats don't go to that extreme.