I might just be missing something(s), but there are some mysteries in the game.
1. When you can't upgrade something (upgrade button is grey), does that mean:
a) you already upgraded it, and you're done? Forever?
b) you just haven't gotten to a point in the overall game where you can upgrade?
c) you just don't currently have the requirements to upgrade? (enough gold? other upgrade dependencies completed?)
2. You should know what you're buying. Mystery items suck audibly. (e.g. gate scroll). In a game like this--one that requires planning and strategy--rolling the dice is really annoying. And then, if you buy it, you don't even know what it does, so have to try it to find out. And then
you have to assume that your understanding of what happened is correct and there isn't something you're missing. Please don't do this with items.
3. You should know what monster abilities do, for the same reason. If a monster has an ability, then you should be able to mouse-over that ability and get a short explanation; maybe not one with exact numbers and percentages, but one that gives a good idea of what you're getting yourself into if you attack.
In the original game, I was able to deal with some of these things by consulting the wiki, but this time around, that info should be accessible in the game itself in some manner.