All depends on the type of item you're trying to create. There is a variety of different sections for creating different items.
For example, sigils, if you want to create a sigil simply copy any old one, change the id to something high, like 70k+ at least, I use 90k+ but those don't work in gshop. You can't have two of the same id, so make sure you keep a log of what your custom ids are. Now to make the sigil work the way you want it to depends on what you want it to do. Let's say you want it to refine up to +5. You need to put a 4 into the 'MAX_R' section, this tells it that the highest item it will work on is +4. Then you need to put a 1 in all of the sections you would want it to work on and add 1 refine to previous refinery level. So in this case +1, +2, +3, +4, and +5 sections would all get a 1 in their boxes. The 'bind' section decides if it should make an item bound after use, I think, not 100% sure on that as I've never changed it, but if you look at other items you can easily see how they should work.
Protection ids are quite important too, they determine if an item drops in pvp or not, or can be sold to npc or not, etc. When making custom gears these are important, but even with all items. For gears is more work. You need to have a model for each different class set. There were 3 before regen, idk if there are 4 or more in regen or not. Before regen they were, balo/forta, rayan/arden/uhh I forget all of the combos right now, but the third one is human and voida I think ,should include celan too, idk, came to RZ looking for something and seen your post lol.
Truth is you need to be more specific about what you're trying to add to get help. Every section has different params that need to be considered.