So let's say you're on a server where houses are available and you want to raise the 3.x million. You don't have maxed crafters, heck maybe you don't have a maxed battle class, here is my advice:
1) If you haven't done so already, assign one of your retainers your main class as their class and start sending them out on ventures. Do long ones at first so you don't have to think about it as much, but eventually you'll want to take a second and check the market board for things that are selling that they can bring back and do those. This seriously only takes a few minutes of your daily game time and it's worth it. If you're like me and have a large time block away at either school or work send them on a long venture prior to that for the materials, allagan coins, and retainer experience
1a) assign your other retainer to either a gatherer you want to level or to another battle class you plan on getting some levels on. Do the above with it at the same time.
2) Do what you can to complete your dungeon and fate challenge logs. Are you a slightly more patient soul? Do the levequest one as well. I recommend that you use the leve quests to level any alt classes you're interested in before using them on heavensward leves as the experience gained in old world leves is WAY better proportionally than the HW ones are. Use or sell (or desynth - see below) the leve rewards.
3) Have you leveled any crafters near 30? Grit your teeth and at least get a couple to 30. Once you do, you can start desynthing items. Wanna know something funny? You can raise your desynthesis over and above things you can craft. As an example, my alt on Balmung only can craft up to level 30 stuff, but she can desynth gear up to ilvl 90.
Why do this? Because certain items sometimes show up on the market board at or below vendor price. Desynth shines when dealing with stuff like this and the materials you get will often sell for more than the item does in these cases.
4) Stop spending so dang much.