General purpose items:
Batfang Headband AC +2 Wis +3 Int +3 Effect: Extended Enhancement II (Increases duration on buffs up to 44th level by 15%) - goes for about 150 plat. Really, this isn't a bad deal. Pretty cheap and still provides some wisdom to increase your mana count. The effect will last you for a long time and 15% duration on buffs means more mana.
Black Alloy Medallion AC +6 Wis +5 Int +5 Effect: Mana Preservation II (Decreases mana cost on all spells up to 44th level by 10%) - goes for about 500 plat. More expensive, but a universal effect for all of your spells. The other Mana Preservation items are pretty hard to come by. This will last you until around 49th or so, when you'll want to look at an Obulous Death Shroud, but those go for up to 12k plat.
If you are DoTing a lot, look at these:
Chipped Bone Bracer AC +4 Wis +5 Effect: Affliction Efficiency II (Reduces mana on DoTs up to 44th level by 25%) - about 500 plat. Again, pretty expensive, but also very effective... and its a pretty solid wisdom item.
Kobold Hide Boots AC +5 Agi +3 HP +10 Effect: Burning Affliction II (Increases damage on DoTs up to 44th level by 20%) - about 150 plat. Crappy stats, but the extra damage can really be nice. It is cheap enough to warrant getting it early.
You can also look at Improved Damage items, but the only one I've seen at a reasonable rate would be a Mammoth Hide Cloak (AC +7 Wis +4 Cold Resist +4), but that only works on spells up to 20th level, so already geatting outdated... you'd be better off saving your money for an Acrylia Studded Cloak (+10 wisdom, among other things). Likewise, there are a few cheaper Improved Healing I items out there, but you'll be getting Greater Healing at 29th.
As for more general items, go to the bazaar, set your parameters, and look for wisdom gear, followed by mana gear. Paying for them is the trick...
I'd recommend the following sources of income:
Karana bandits: each sash can be returned to South Qeynos for a bit of XP (probably none at 24th) and a bronze weapon (1.5 plat or so, on average). They occassionally drop bronze weapons, as well, and are pretty darn easy at 24th. Only the brigands will be blue, and they are relatively rare (and easy). It is *difficult* to make more than 35-40 plat per hour this way, but it is safe and never camped.
Spider silks: You've probably already been told about this. Crag spiders in East karana... you'll have an edge with tracking, but it is still fairly busy. You can sell them in the bazaar for around 10 plat per spider silk. Other spiders drop silk, too, just not as much. I managed to save 25 pieces while getting a level or two in West Karana, and sold them for 250 plat.
Split Paw Gnolls (outside the spires in South Karana): You would have a darn hard time solo'ing them at 24th, but by high 20's they aren't bad. Snare, DoT, and DD if you have to. Group if you can. They range from 25th to 29th, can be single-pulled without harmony (though you do have that wonderful spell). They occassionally drop fine steel weapons (you can see which are armed). The ones with whips have a Gnoll Hide Lariat; it only sells for around a half plat, but can be sold in the bazaar for a few plat to higher level pet classes. The ones with daggers generally have daggers of dropping... these are less sought after, but still can be sold in the bazaar. They drop up to 3 plat or so in coin, too. I generally make around 100 plat an hour here, sometimes more, just depends on the group/traffic.
Of more importance, they drop a few items you can use... split paw hide gloves (wisdom item), belt (mostly saves), tunic (saves), and mask (saves). Really, if you don't have better, they aren't bad. The gloves, in particular, are pretty nice for a druid.
Hope that helps.