Have you thought of the best way for you to prepare for the Expansion Reaper of Souls? If you do not want to lag far behind other players, you should take one investment at least. Currently, there are four main investments, hoarding crafting materials, gems, high-end auction house items and Diablo 3 Gold. Which one would you take?

Hoarding Crafting Materials: When the D3 AH close at 3/18/2014, you would craft items instead of buying items. No matter if it is for yourself use or the investment before the expansion, it would be the safest way to prepare for the ROS. Account Bound items like Bracer, Amulet and Gloves all need Demonic Essence as well as other common materials. You can not exchange Demonic Essence. But you can exchange other materials.

Hoarding Gems: When you have a new class, for example Crusader, you would need the Green Gems on the weapon to have the 110% critical hit damage. But if it still need several thousand to craft one, you bet more players would need it. But I do not think this would happen. In the expansion, it is more likely to have several dozens of gems to craft a epic one like in the Console version.

Hoarding High-End Auction House Items: Although level 63 items would be less valuable compared with those level 70, players do need items to transfer from level 60 to 70. If a lot of players come back, they would need supporting items as they have been away for a long while.