I have pans, Wilton colors, a palette knife, a turning cake stand thing, i use ziploc bags for piping.

What else should i have on hand?

i'm planning a trip to the cake decorating shop but i don't really know what's what.

P.S I like making 3D cakes

Thanks for any pointers

tips; I'm a decorating tip junkie. You will need several of the one you use most if you're using more than one color so you don't have to stop and wash up.

cake leveler; for torting and leveling

those are the most essential items

????
What is your question? You are too vague.

Cake leveler, fondant smoother, cake icer tip, extra tips as mentioned before, fondant tools (bone tools). I use the fondant tools alot. Are you just starting out? Are you going to be doing any icing flowers? If so...I'd like to add a foam block. You won't realize how handy they are for putting the flower nails when working with them. What a huge help!

In addition to what was already mentioned: fondant rolling pin (small and large), cornstarch puff, shortening, icing/fondant colors. Oh, I could go on and on!

It's not possible to have too many couplers, heat resistant rubber spatulas of various sizes, and a good serrated knife. I always find new things I need at the cake store, regardless of what I already have.

Large offset spatula, small offset spatula, bench scraper, VIVA paper towels, tons of toothpicks if you're using Wilton colors ( I prefer Americolor myself, but occasionally still use some Wilton ones), disposable decorating bags, flower nails (to use as heating cores, and for piping flowers onto), bake even strips, parchment paper, and Sugar Shack's DVDs.
There's more...but this will help you part with some of your hard earned cash...

What about petal and luster dusts and pearl dust for enhancing the cake after its compleated and for the flowers! Flower cutters and veiners.

Get rid of those ziploc bags Use pastry bags. 8" and 10" the most; then some 12"s.
A quick icer tip and a 16" pastry bag to put it in (for applying b'cream).

I find I use knives alot and I just relegated a small set to our cake kit. I like the cake levelers, but since I can't afford an agbay just yet, can't beat the good ole serrated knife to level a big cake.