I really think that buying upgrades with angel investors should decrease the price of the next angel investor. All time cash earned should give the same amount of angel investors, no matter how many you have spent. I realize that this would mean you would get a refund of angel investors once a product was bought. But you could counteract this by readjusting the price of the angel investor after a soft reset is done.
@dragon34 For 33 your number one priority is getting and keeping the space rings. Use the warps to directly attack the rings and avoid fire. First get the left ring, then the right one. Once you have both, the black army should be coming. But killing them will be a lot easier with the rings. So use the ships in the rings to clean up the center planets. Once you have the center, you should be able to hold it by sticking some ships in the right ring. Then clean up the left side. Once you have the left and center, attack the second warp. Now you should be able to keep both sides and get the right side. Also, when attacking something wait until ships leave it. You will lose planets, that is ok, the rings are more important.
@Cyrillin The first update was screwed up. I went from about 200k angel investors and missing the 300 awards for some items to billings of angel investors and at least 400 of everything. It got fixed though, so the growth rate is now a lot slower.
One complaint that I have is that coal is used for both iron and steel. I have a lot more iron than steel, so steel isn't really useful for upgrading. But smelting does steel first, which reduces the coal available to smelt iron.
If you are wondering what to spend copper on, you should upgrade your sword. Level 1 copper armor is disappointingly bad compared to upgraded leather armor, but the level 1 sword is pretty good. And you will need wood for smelting copper.
Here is a link to an image with all the endings if you are missing one or two. Completing parts of the map will introduce new choices on boxes you've already seen though. http://i.imgur.com/E0F85Ip.png