Well first of all, Optifine.
Journeymap: for a minimap
Biomes o' plenty: for more biomes.
Aether mod: just because.
Dynamic surroundings mod: if you want better minecraft sounds.
TekTopia villager mod: Better villagers and villages, you can even create your own village!
Just enough items: Just a handy mod.
Infernal mobs mod: miniboss mobs? With cool loot ofc!(like in hexxit)
Twilight Forest: yes.
Damage Indicators mod: almost every mod-pack has this mod, and it's very handy.
I could add more mods, but I guess that this is enough for someone that is new with modded minecraft.