My advice would be in general terms - not build specific and not class specific.
If your basic gears are tier 4, or/and level 60+ runewords. I think you should focus on leveling up to 115 in order to start grinding some random but useful set items. Three options if you have really good gears: 1) Want to have some fun? Secret Cow Level 2.) Need gold? Go to Island of the Sunless Seas 3.) Need Signets of Learning/Gold? Go to Torajan Jungles or hunt Nihlatak for Signets of Learning(I've read somewhere that there is a limit on how may times you can grind there, by the way he gives 2 signets per run).
IMO, it will not matter what you do next as long as you can keep the kills rolling - level 100 areas have the chance to drop set items. If you can't breeze through any of the options given above, grind some experience and gold from regular mobs (found in level 100 areas), then upgrade your regular runewords if you find no useful set gears to equip.