There are hi-res texture packs & mesh improvements that are pure wins, even for a first time player, IMO. They don't change the art much, they just make it look way better on a modern screen. And I'd recommend a mod to make plant harvesting more like the later games (there are a few, I think the one I usually use is Herbalism—the vanilla behavior of treating them like containers and not marking which have been harvested simply sucks). Plus the usual unnofficial-patch mod that's basically required for any Bethesda game.

That'd be the extent of the mods I'd recommend to a first timer.