Might be helpful if you told us what you haven't quite grasped yet.
A few hints (tl;dr alert):
(o)Especially on higher difficulties it is preferable to make one's own custom race.
Suggested Picks (meaning, the ones I use mosto f the time (-:
Cybernetic - Eating 50% Production and 50% food is a mixed blessing, but allows you to ignore farming (useful, cause you can feed a whole world using Hydroponic Farms and Freighters. Later in the game,
Creative - must pick on higher levels, imo. Unless you want a challenge. It's a totally different game if you cannot research *everything*, so you might try some time what it's like to have to exchange technology on a regular basis.
Subterranean - Additional space on planets is great, as it boost your overall empire effectiveness.
For penalties, I say it's safe to go for ground combat penalties, perhaps handicap you ships a bit.
Food production penalty is good coupled with cybernetic (or lithovore), growth and income penalties can be fixed with research and setting a few planets to bild Housing/Trade until desired results.
Good but not stellar picks:
Different governments other than the standard Dictatorship are nice, but each has its quirks. Unification, on the one hand, would be perfect for max production race, but it invalidates morale bonuses (and penalties to be fair) which, later in the game can give above 50% efficiency bonus
TheMocracy gives muniez and the all-important research, but comes with an espionage penalty, for which you have to compensate asap.
Feudal comes with a penalty, because it handicaps research. Though it an be interesting for a ship aggro game.
Home world improvements - they are cheap, so feel free to give yourself an edge while buiding up, if you have an extra point or so.
Picks I'd Avoid:
This is just my personal opinion, but I find Lithovore overrated. At 10 points why not pick unification and a bouns to production?
Repulsive - problem is, it simplifies diplomacy (which is already quite simple). Why dumb down your game more?
Uncreative - Research is uber in MOO don't handicap yourself that way.
Research & Production penalties - this can be made up for, but you're essentially crippling your early game. Not good.
Production bonuses - this may be just me, but I don't find them that useful, outside special circumstances. Also, you can quickly research buildings to simulate these effects (and you'll get plenty of opportunieties to reasrch such upgrades for yourself, so that a meager +1 might go unnoticed in the long run) .
Overall: look for combos and capitalize on them. See what it's like to have a race with bazillions of cash with Income bonus + democracy + fantastic taders, or a Unification + Production bonus + Cybernetics production behemoth.
(o)This game rewards research big time. Invest in it a lot, ideally have all your "poor" planets focus exclusively on it. Avoid penalizing your research at all costs. Uncreative IS a crippling drawback
Things you'd rather research early:
Battle Pods - the extra space is imperative to design a good ship.
Automated Factory & Laboratory - so that you get a slight edge in both areas. Plus, they're really low on the tech tree.
Terraforming + Radiation shield - so that you can colonize any planet except for toxic.
Titan & Death Star construction - for the ultimate ships.
Tachyon Communications - for the added bonus that lets you have more ships without maintenance.
There are other, even more important ones, notice how the choices become even harder if you are not creative - should I get the better factory now, or trade for it, or wait until I can research the better one. etc.
Overall, if you're planning on fighting a war, focus your effort on better weapons (beam weapons or missles, there's many choices), otherwise choose resaerch that upgrades the area you feel is the most lacking at the moment. From experience, unless you need some boost in Diplomatic ability, you can ignore the Sociology branch.
Different research usefulness also varies from game to game. In a small galaxy, with lots of asteroids and gas giants, Planetary Construction is invaluable.
(o)Leaders - they are unfortunately random, but can really aid you in your early game (and their bonuses become massive later on). Decide what you need most at the moment, and plan ahead if you want to specialize whole star systems.
It all depends what strenght and weaknesses your race has, a spiritual bonus is worthless for Unification governments, Megawealth can fix your finances early on etc. etc.
(o)Spying. Don't neglect it. It can help you get an edge in research, and can also help win a war (by disabling a pesky star base for instance). You can even make two empires fight one another by framing them. Even if you don't want to do these, be sure to have a tight spy network. Messages that someone just stole your hard earned tech are plain annoying (and the sole reason Darloks don't survive long in my games).
(o)In ship design, it is simple. If you have bigger guns and bigger ships, you win. You should look for combos, just like in race design. Some are more obvious, some are less.
A few examples: Good shields plus Shield capacitors, Cybernetic Race plus Automated Repair Unit and Advanced Damage control for really tough ships.
Or, the component that doubles damage bypassing shields plus weapons with Shield Piercing Modification.
Or the uber combo of two components (at the end of Field and Power trees): one enables you to cloak your ship with 100% efficiency, but you have to skip the turn, the other which allows you to take two turns in a row.
(o)Don't neglect your protection, the AI will exploit it (especially on harder difficulties) and either backtab you with superior fleet or do agressive espionage. So have both bases covered.
And, best of all, have fun. There's lots of opportunities to do it in Moo2 - experiment with different combos and difficulties. There is a whole new level of fun, when you play as a physically puny Psilon, quickly rush some tech to crush nearby Klackons, then use them as cheap labor in your factories.