Location: Gadir (Atlantis)
Closest Portal: Gadir
Noteable Loot: Almost every blue/epic/green item that can drop in the game from TQ/Immortal Throne
In my opinion the best way for you to get gear in Titan Quest is by using Pantheras in Gadir. Pantheras is an NPC that was added into the game during the Atlantis Expansion Pack who will take your hard earned Gold and transmute it into orbs of good loot for you. Typically in games this sort of thing sucks and never gives you anything good but in Titan Quest the loot it gives you is amazing.
Each difficulty unlocks new type of Orb that you can buy; at Legendary the cost of the Orb is only 5,000,000 Gold. Normal the Orb is 1,000,000 and it will still give you worthwhile loot if you're on Epic or Legendary difficulty. Essentially the only items that the Legendary Orb can not drop are Monster Infrequents. There may be a few very high end items that the orb's loot table does not have access to (like the Freyja's Set) but I personally farmed thousands of these orbs and got almost every single item in the game. I know this because I use TQVault and kept a single copy of every Blue/Purple item that I got as well as every Artifact Recipe.
My advice to you would be to choose a farming location from my Titan Quest Farming Guides and grind for gold. Use a character that doesn't have to chug Potions non-stop to make the most money or pick an easier location for whatever character it is you are using.
Keep in mind too it's not like you can only purchase the best orb to get good loot. You'll get plenty of great items with the Epic and Normal orbs too that will last your character well into the high levels.