There's no "best" set of picks. What you should pick depends on your playing style and the map. If you enjoy invasions and wars, you should pick weapons or soldiering. If you want a peaceful game, you should pick diplomacy. And so on. On large maps, speed becomes valuable, but it's not that worthwhile on small ones.
Some popular picks are speed +1, planet quality +5, diplomacy, economics, morale, population growth--you really can't go wrong with some combination of these, and they will help you no matter what your playing style is like.
There *are* a few picks which it is generally agreed are pretty worthless--I've never heard of anyone who liked "courage" or "espionage." There are probably a couple other worthless picks but I can't remember them offhand.
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