Net points are the amount of points that your village/empire is worth. To check how many points your village/empire is worth, go to map. The number is displayed under your name. After having played this game for an evening, I have 650 points.
You get points for upgrading/construction buildings, researching things and recruiting soldiers. The most efficient way of doing so is by following the quest line, and by allocating all of your workers to gathering resources. The more resources you have, the more you can build.
A quest for reaching 200 net points and a quest for reaching 500 net points have already come by, so also for this achievement you need to have the quest unlocked. These quests showed up in the quest tab furthest on the left for me.
The amount of points you get is calculated like this:
1 net worth point =1000 gold / 1000 wood / 1000 iron / 1000 stone spent on buildings or research
1 net worth point = 500 gold / 500 wood / 500 iron / 500 stone spent on army recruitment.
So it seems as if spending resources on recruitment is twice as efficient as possible, though for completing quests you have to research things and construct buildings, so I advise you to do more of these (since completing quests earns you resources, which you can spent on completing more quests, earns you more resources, and so on).
After the quest for 20k, one for logging in and out for 14 days will show up.
Thanks to Shadow Kisuragi
for adding information.
...to be updated...