My favorites:
1st is the chisel and bits mod because this mod allows you to build anything with small cubes that are called bits. 2nd is the carpenters blocks mod because you get more blocks (that are realistic) to use and for me that is really helpful for building bases. And 3rd is the biomes o' plenty mod because it definatily gives you more biomes. And 4th is the Sildur shaders, what these do is they give your whole gameplay a more realistic feel with enhancing many textures. This nexr one isnt a mod its a texture pack but trust me you'll want it, it is called "ultimate imersion"
Most mods add content to the game to change your gameplay, change the creative feel, or give you more options for how you interact with the Minecraft world. Most people who create mods for Minecraft (modders) use Minecraft Coder Pack and either Minecraft Forge or Fabric to make mods. Some mods might be bigger expansions, while others add more settings and options to make gameplay speed better, graphics, or gameplay of the game.