I believe fitasc is right. You need to stop and read your manual from the beginning. The lee manual is very good beginner manual to learn from.
It sounds like your talking about the lee dippers. That comes with a lee loader and the lee die sets. It is nothing more than a volumetric mearuing device similar to measuring spoons your wife might use when making a cake or food recipe. Very good devices i like them very much. Very safe. however you still need a scale to measure it on. I don't like the lee scale personally but it will of course work if u have it.
If it is the lee powder dippers u need to use your manual and look up how much volume the cfe pistol takes per scoop and do the math to equal the number of gr of powder needed. Here is a webiste that explains how to use the lee dippers
http://reloadboss.com/lee-powder-dippers/
Case life has varying factors including but not limited to how many times loaded, gun shot out of, type of load (heavy or light), weather when shot,etc. I have some 9mm brass that has passed a dozen loadings, and ive seen factory ammo split the neck on the first shot. It can be a crapshoot.
Next if u are using hornady bullets i would suggest getting a hornady reloading manual. It will have the specific bullet u bought and what powders worked best for it. Lee manual uses recycled info from manufacturers websites and books and may not have your soecific bullet.
Lastly, stop and read the first 9 chapters of Lees book. I say that because i want to make sure you are safe as possible while learning because a mishap can cost dearly.
To answer your last question as i understand it, yes if you have "any old" 9mm Parabellum case the 115 gr .355 diameter will work provided that:
1. The case is in good condition to be fired again
2. You use the correct primer
3. The correct amount of powder is used
4. The bullet is seated to the depth according to the proper reloading manual.
Get those 4 things right and every thing will be hunky dory. Happy loading and be safe!