New Users - Important Mods Checklist

[JohnFromGWN]

As a "new to GTA5 modding" user you have likely installed the absolute essentials: Script Hook V and OpenIV. Now let's take a closer look at what you've installed, where, and why.

TL;DR: These are the files you absolutely should have, almost all will be in your game installation folder:

dinput8.dll (packaged with Script Hook V)
HeapAdjuster.asi or GTAV.HeapAdjuster.asi, (install one, not both, refer to recommended one with chosen gameconfig.xml)
Menyoo.asi, or TrainerV.asi which is Simple Trainer. Trainers are amazing, your could choose one of many, or install more than one. You don't need to install NativeTrainer.asi which comes with Script Hook V.
NoBoundaryLimits.asi
OpenIV.asi
PackfileLimitAdjuster.asi
ScriptHookV.dll
ScriptHookVDotNet.asi (and its associated xml and dlls)

The last essential file is the gameconfig.xml and there are several options. Read below.

Now let's review what files and mods should be in each important to modding folder.

Your Game Folder

Call it the game folder, the root folder, the installation folder, the GTA5 folder - whatever you want - this is the folder that contains GTA5.EXE and where the magic begins.

Script Hook V
Once you extract/unpack the ScriptHookV zip you will see a folder called bin. Inside are three files. Ignore the one called NativeTrainer.asi and place dinput8.dll (aka asiloader) and ScriptHookV.dll in your game folder. These are the two files that make modding possible. There is also a RAGE Plugin Hook (RPH) which is popular with some GTA5 communities. Never use the dinput8.dll from the windows system32 folder.

Open IV
When you install OpenIV you are presented with the GTA V - ASI Manager during the installation. It offers you 3 options.

1. The ASI loader. You can accept this but if you installed Script Hook V first, you already have it because the ASI loader is dinput8.dll. This file is essential because it loads all files with the asi extension including OpenIV.asi and your Trainer and many others.
2. OpenIV.asi. This is the plugin packaged and installed with OpenIV (the editor/program) and will load the addons in your Mods folder (your dlcpacks). Again, this file is essential unless you mod the game files and folder directly. You will still need the program itself to make edits.
3. openCamera.asi. This file isn't mandatory to install but it can't hurt. It is only used in combination with the Rockstar Video Editor.

Heap and Pack Limit Adjusters
The Heap Limit Adjuster or the HeapAdjuster mod (install one only, not both) and the Packfile Limit Adjuster are essential if you are installing addon mods. Without them, always used in combination with a gameconfig.xml mod, your system is very likely to crash, even with a single vehicle addon.

Trainers
These are by far the best mods you can install. Read more here.

ScriptHookVDotNet
Mandatory if you want to run installed script mods or scripts of your own. Not to be confused with Script Hook V.

NoBoundaryLimits
Wonderful plugin that is mandatory if you want to install addon worlds and maps. As the name it implies, it significantly extends the size of the GTA5 open world.

Other Mods

gameconfig.xml
One of the most important mods, for stability, is the gameconfig.xml file, which is available as a customized mod. Contrary to the other files mentioned above, this file requires OpenIV for installation. It is located here root folder\mods\update\update.rpf\common\data.

Note: the gameconfig.xml mod is actually a replacement for the game version.

Dlclist.xml. Although not strictly a mod, this editable file is critical to modding. You can read more about it here.

NativeUI.dll (only file mentioned here that goes in the Scripts folder, no longer supported but still required by many mods. Slowly being replaced by LemonUI.)

BEWARE

Certain mods, particularly those with OIV installers, can overwrite your gameconfig.xml with an older version - reverting your updated one to one that is no longer appropriate.

More about what modding files do

Troubleshooting Help

[JohnFromGWN]

Please check to see if the following files are in your game folder. Most of these are essential or highly recommended.

Click on picture to see larger version.