Requires the library mod Collective.

This mod is part of The Vanilla Experience.
Starter Kit is a mod which allows players who join a world for the first time to receive items set in a config file. It's possible to set items to any specific slot in the inventory, to the offhand and to the armour slots. The mod can detect which players have never joined before. If players have joined prior to the mod's installation, it will only change the inventory if it's completely empty and if the player again first logs in near the spawn point.

Can be used in a server for all new players or in singleplayer to start off with a default inventory of your choosing.

Commands:
/starterkit set - Sets the starter kit config file to be a copy of the inventory of the player executing this command. The old config file is kept and renamed. Requires cheat access.

The default config file, located in /config/starterkit/starterkit.txt:
--Or use '/starterkit set' in-game for NBT tag support.
Modded items are supported, the format is modid:item_name. The amount can be set as -amount after the item name. See bread below as an example.
For the inventory slots: 0-8 is the hotbar, 9-35 is the inventory starting in the top left.

And the result on first join:

Starting in version 2.0, it is now possible to write an entire inventory to the config file. NBT tags such as enchantments and written books are supported.
The written book:

Running /starterkit set, which writes the entire inventory to the starterkit.txt config file:

The inventory of the last image results in this config file:
Located in '/config/starterkit/starterkit.txt'.