You may have already figured this out, I'm mentioning it because you haven't mentioned it, just in case. Hope it helps.

Enchantments get more expensive to put on the more you already have piled onto an object. Before starting it's usually good to compare the cost of each enchant applied and then put them on in order of most to least expensive. That way the least expensive will be expensive by the time you get to them but hopefully won't have gone over the limit of how many levels you can use to apply it.

Easy way to get God armor:

1. Repair the end grinder

2. Use the end grinder for XP

3. Take 3 or so of the item you want to enchant (ex. Diamond Helmet)

4. Use the enchantment table to get what you need, if there is nothing, enchant some random thing to clear the options for the helmet

4. Repeat this until you have the best enchants, less than five minutes spent and I have God gear using this method.