Where to gear up as an elemental (windy) druid?

Unless you're going to farm for runes or socketed maces, there's no reason for you to stop progressing if you can.

There is very little in Nightmare that will help you, item wise. Your end game hell items are rune based runewords for spell casting druids.

You need to farm runes (hell sewers) and torches (hell boss farming). Level 60+ in nightmare, you should do as many +players as you can if you're farming in nightmare. Just because something didn't drop for you with +players, doesn't mean it's not worth it to do.

Diablo 2 is all about that grind, so keep at it!

Let's start with some easy methods to buff your gear:

Lore - OrtSol - Helmet: +1 to all skills, %30 Lightres

Smoke - NefLum - Armor: 50% to all res

Spirit - TalThulOrtAmn - +2 to all skills, some nice stats

Rhyme - ShaelEth - Shield: 25% all res, cannot be frozen, 25% mf, faster block rate

Ancients Pledge - RalOrtTal - Shield: 50% all res

You can easily kill nightmare or hell countess to find most of the runes. From the runes above only Lum and Shael might be somewhat hard to find. But do around 10 Hell countess runs on players 1 and you should be good.

Most of your good gear will come from Hell Mephisto. So you should get the basic items up and get yourself a good map. How do you do that? Mephisto is in Durance Level 3. Your waypoint is at level 2. It should be close to the entrance to level 3 and that is considered to be a good map. You reset your map by switching difficulty e.g. going from a hell game to a normal. So once you found your map, you should not reset it. At hell mephisto you can find things like Shako, Skin of Viper, Stormshield, Maras Amulet, Stone of Jordan and all the good stuff.

If you don't care so much for your character and want to gear up quickly in general, you should consider creating a mf character, that is able to quickly teleport and kill hell meph. The items you find with her, you can later use on your druid.