the best level to farm is the one before octopus, you can beat it with all modes on and get lots of xp (its easier with romans, not sure if works with chinese)
lv 4 is hard, and longer, but if you build 3 more heavy lasers u can handle their big ship reinforcements, and slowly your ships will destroy their base
some ppl said they wanted to see how infested are the areas without having to click one by one, to do that u just need to click the three colors rectangles under the stats menu
about the plundering, the best solution i've seen for it so far is: max your temp storage cap(upgrading your mines and the temp storage tech), see how many resources you will need (for upgrades, soldiers...), if the temp storage res are enough, take the necessary amount; if not see if u can take another resource and trade it on market for the needed one; if not, finish dungeons(looking for res, as long as you dont spend extra dungeon keys) and see if it's enough; if not, use res cards; if still not, plunder someone; if still not, dude, wth are you doing?
well i dont spend money on game so i cant say how it is with the gold system, 2nd: ppl who like this game normally are playing right now, since the game have chat and ppl will rather use it, 3rd till now i havent got any glitch and great lag problem, again, i cant judge this problem. so basically i'm enjoying the game, if u dont like what u see close ur eyes then
if you are finding hard to beat nagoya and the special katana skill, just go without armor and that skill will not damage you at all(but beware the normal attacks)