Its best to keep your mobs green until you master your comp and develop a strategy. I started going to SM around 32 and my comp is Pal, Piest, 3x mages. You can do the last wing of Gnomergan, there's a rare that spawns that has nice loot, Thermaplugg has nice loot. Get your Acidic Walkers and Hydrocane for your casters from Irradiated Horror. RFK has some nice drops too.