StartingInventory Mod 1.8, 1.7.10, 1.7.2 is a mod that makes it so when you start up a new world you will start with a few items in your inventory. You can set what items (and how many) you want when you start just by simply editing a .txt file in your .minecraft folder. To tell this .txt file what you want to be starting with just type in the id number for that item, then a comma, then type the quantity for that item you want. You can add multiple items just by doing a new line in this .txt file.
Install StartingInventory Mod
Requires Minecraft Forge. Do not extract. Drop the downloaded zip file into the mods folder in your .minecraft folder. Make sure you have also downloaded bspkrsCore, a REQUIRED DEPENDENCY for this mod.