What are the must have mods for someone starting?

[SlyFrog]

I'm just starting out. At the same time, I like to play the "best" version up front. I don't have time to get used to the basic game and then add mods in, as that simply means I will have some time to play the basic game and never get to the mods. So I might as well spend limited time playing the best "total" version.

At the same time, I don't want bells and whistles just for their own sake. I'm really looking for things that make the gameplay better (so I don't care about graphics packs, for example). The mod list can be small (or none, if no mods really make the game substantially better. I'm just looking for the key mods that give things like better AI, substantially better UI, etc.

Thanks in advance for your help.