I would advise to stay away from Vana as a GX unless you plan to use it for other characters.
Rideword hat is better for HP leeching which is useful for Nightmare Toy Factory, especially if you don't use reductions. plus its cheaper than Vana
Evil dragon armor is nice but with Thanatos Katar, RWH, and malicious set/tengu set, and succubus(optional but helps) you should already have enough leech so Fire Dragon Armor would be better for more hit rate and to make up for the extra slot you lose by using Thana Katar. but a nicely enchanted nab(FS9~12) always works fine.
You should already have everything you need for leveling a GX to 175 even without OCP gears, but looking ahead it would be a good idea to invest in some of these headgears:
+9 Happy Flapping Angel Wings- for leveling past 175, not really necessary though i guess
+9 Faceworm Egg Shell- Necessary for doing faceworm in 12 minutes or less for those good skins.
Tengu Mask- half of the tengu set and currently at a low price, can get the other half later when it is rereleased
Toy Syringe- useful, not too expensive and can carry you until tengu scroll is rereleased
Alternatively can just use Mob Scarf and glasses combo if you have the funds.
For accessories I cannot think of one that is a game changer worth spending zeny on at the moment, besides PDM, but good ones to consider depending on budget is:
-Giants Protection: definitely the best, but worth just waiting for it to be rereleased
-Bakonawa Tattoo
-Kirin Horn
-Keranos
-Assassin Despair
-Vesper Core 04
can also just stick to Rogue's Treasure