I'm no expert, but there don't seem to be too many people playing Nova anymore. Thus, I'll try and help you out. Also, I am assuming you are playing agaisnt the AI.
In Nova, it is rather difficult in the beginning since the Firebird income is so limited. You'll need to raise taxes (though not so much as to make them rebel), maximize the tithe skim and reduce unit pay (use this as a last resort, though), or just disband several units.
Also, building lots of structures on a planet where you control the palace increases your tax income. Just watch your food income, as each structure requires a certain amount of food (I think) each turn.
Money aside, the main resource you need to heavily micromanage is food. The other resources don't matter anywhere near as much, although lack of them hinders the construction of new units and such. But food is always required, and is required by pretty much everything (not necessarily to build, but to maintain).
I haven't tried all the houses, but food income at the beginning of the game is usually not enough to sustain what you start with (though there is enough of a stockpile to keep them fed for a while). Scout out prime areas for new farms and capture any rebel farms you can.
Food aside, metal is the second most important resource in the early game. Find good locations for mines and have an engineer build them (but concentrate on having a positive food income first) whenever you find a good spot. These are usually on flat land near mountains and oceans.
Once food and metal is taken care of, move on to energy. This is required for all of the resources that you have to make yourself.
As for the other resources, it depends on which units you tend to build. See what the various units require to build and go from there. In the early game I tend to produce mostly Infantry (which you have at the start) and Heavy Infantry (after I have researched them). Infantry require food and metal, while Heavy Infantry require the same amount of food and metal as well as some chemicals and electronics.
As you are able to build more types of units, include whichever you like.
With diplomacy, it doesn't really matter. Outside of some space engagements you don't have too much to worry about when it comes to war with someone else. Of course, it all depends on which galaxy you may be running. In the default EFS galaxy you have no real threats on your home planet besides some rebels scattered around. It is when you have forces on other planets, particularly the home planets of other House factions, that you have to beware of war.
War aside, diplomacy can gain you more tech or money, if the AI agrees. You can also try to get other factions to vote for you, or get them to promise you a particular ministry if they are elected. With the Stigmata garrison in your control, you get a boost of resources and units. The Imperial Eye and Imperial Fleet don't really give you much in the way of resources in the default EFS galaxy, and the Eye is rather useless. But the Imperial Fleet gives you a nice bit of firepower you can use on whomever or whatever you like. Until the ships are destroyed, anyway.
Not sure what else you're unsure about. Anything else specific?
- <font size="2" face="Verdana, Helvetica, sans-serif">Food and Firebirds (money) are the most important resources.</font></li>
- <font size="2" face="Verdana, Helvetica, sans-serif">Metal is also important.</font></li>
- <font size="2" face="Verdana, Helvetica, sans-serif">Other resources depend on what you want to build.</font></li>
- <font size="2" face="Verdana, Helvetica, sans-serif">What units to build depends on what you've researched and what you're facing.</font></li>
- <font size="2" face="Verdana, Helvetica, sans-serif">Diplomacy can get you new technology (if they have something you don't), money, or votes/a ministry.</font></li>
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All that aside, it all depends on which galaxy you are playing in. The default EFS galaxy differs quite a bit from most galaxies. Other galaxies are usually more difficult, but can give you better resource production in the early game.
Of course, with Nova it is rather difficult to find non-Hyperion galaxies (they aren't compatible, as far as I know) to use with Nova.
Finding a different galaxy to play against the AI with is even more difficult (if you want them to actually do things).
I believe Fadingsun.com was the best place to get galaxies, but that site is unfortunately dead, as are most site links I've checked here in the forums. I've been looking for other sources, but haven't found any yet.