I can't seem to use the said mod. As I seem to lack the folders required for the use of this mod. Is there any other solution or am I doing something wrong here? I tried extracting the files unto the GOG > Baldur's Gate 2 map, but it keeps saying that it's missing certain files. So either I did something wrong during the installation of BG2 and 1...or the BGT mod isn't compatible with the GOG.com versions.

Edit: Nevermind. It's fixed now.

Have you read the Readme or checked the BGT forum over at Spellhold Studios? They've plenty of help for installation problems. Things to remember (from the BGT readme):

You need a clean, custom install of BG1, meaning all boxes checked when installing, and patched to version 5512. The GoG version is the Original Saga, so this shouldn't be a problem. *Do not* add any mods, not even a fix pack.

You need a full install of BG2, with the Throne of Bhaal expansion, and patched to version 26498. This can have some mods, but I'd recommend none since you seem to be installing BGT for the first time.

They also recommend 4GB of disk space be available to install the game to.

Extract the BGT-WeiDU mod to the BG2 directory.

Beyond this, I'd suggest viewing the readme file for specifics, since it requires different handling depending on your operation system.