There still aren't any official tools for mod creation or a universal way to add mods to your game, so modding GTA 5 relies on third-party programs. This is where things can get a little sketchy ...
Supported by Terraria developer Re-Logic, tModLoader is easy to download as a free DLC on Steam. Most Terraria mods will work with tModLoader, but it’s always worth checking the individual mod ...
All the Mods 10 includes hundreds of mods, including some of those listed above. That said, it’s a pretty hefty download, so you might be unable to run All the Mods 10 on a lower-end PC.