But it's been asked time and time again... "Where do you get these items?" and "Where do I get XXXX ore from?" So here is where I try to shed a little light on that.
Levels 1-4 is where you can get some items. They show up in the Boss chests at the end of the level. Of course it is random and not every map will give an item, but this is where you get them. Just farm these maps till you get all your Heros setup with items. I personally found that the second level of Tower, "Frozen Ice", is the best place to get them. I just farmed "Frozen Ice 1" over and over (and over and over and over.....) till I got all the items I needed. Try not to move too far up the tower till you have a full set on each Hero, the items will really help out.
The rest of the levels offer "Create" materials needed to upgrade your items. It's simple to think about what you are going to get on each level.
Level 5 offers up "Tin Ore" that is used for upgrading basic level weapons to Green Weapons
Level 6 offers up "Light Leather" that is used for upgrading basic level armor to Green Armor
Level 7 offers up "Agate" that is used to upgrade basic level jewelry to Green Jewelry
Each level after this repeats this same pattern but offers the material needed to upgrade to the next level of item.
The Tower itself is a maze. Since there are a limited number of moves you can make before you have to spend gold or just wait for the turns to recharge it's best to find the boss as quickly as possible. To this end I have started putting together a tool that will allow you to "find" the map from other maps I have already mapped out.
Edit:
This domain is no longer owned. however....
Here is a new domain hosting the tower maps.
http://aoetower.clruckman.com/
To use the tool, open it, and click the starting point. As you fill in the details the "Map Matches" at the bottom will show if the map you are entering is found in the system. You can click the map number at the bottom to show that map. If you want to get back to the map you were entering click the "Revert to Working" button. Once you have completed the map you can use the "Reset" button to blank out the map and start over. I have added the map backgrounds to make it easier to place the starting tile.
If you got any questions feel free to post in the comments and I'll answer them.
Good Luck in the Tower.
-Demotis