Pure caster druid is fine and the builds are all about what you would expect: i.e., max WIS, load up on metamagics and Season's Herald PrE, slot your Spellpower gear, blast away.
Druids don't get the burst DPS spells that, say, a Fire Savant does; they focus more on DoTs like Creeping Cold, Ice Storm, Wall of Fire, etc.
Melee druids are also fine, though here it gets more complicated depending on whether you want to be a shapeshifter or use regular melee weapons. If you want to make use of those staves you've accumulated, some sort of rogue / druid MC is the obvious choice; also gets you trap skills & Evasion. Either STR- or DEX-based would work too, thanks to DEX to dmg from Acrobat cores. WIS staff builds are trickier, since AFAIK there are only two named staves which get WIS to dmg (
Inner Sight,
SotS). The latter is preferable due to higher base dmg and larger crit profile, so if you don't mind farming Ghola-Fan (or can find it on AH), good luck.