You, and everyone else, only describe skills related to ships and fighting. But if you want skills that "...just keeps giving" there are a lot of care-bear skills to go around. ISK is life, and so much more than cap. I myself would go for this one, since it's good to get you going when you start playing EVE and you can have it on each character in your account generating ISK. You can train this one to lvl 5 and Interplanetary Consolidation to lvl 4 within the 100% bonus speeds. So you can get it for your two extra characters on the account quite quickly. The skill is:

Command Center Upgrades: Passive ISK-income. Why the dodo not?

Werner Lucifer