I play on masochistic, and I almost never build any military ships until I've got medium hulls. I like to build up basic infrastructure first, then build medium hulls and attack the weakest adjacent civ. With diplomacy and bribing them to war upon each other, I almost always stay at peace until I
choose to go to war. I usually form an economic or research treaty with one close-by potential threat, because it almost always prevents them from declaring war on you. If there are any minors close by, I take them out first, because you're essentially getting another homeworld quality planet, with the civ-capital colony tile. I also make sure I trade all the minors the necesary techs so they can build all the capitals, because sooner or later those capitals become mine.
I usually dont launch an attack at a civ until I have enough to assault multiple systems at a time, but if a civ is growing too fast I may attack them earlier and pick off stray planets. Once I'm at war with someone I don't stop until they're annihilated, except for some very rare situations. I try to fight only one war at a time, but as the current one nears the end, Im assembling the strike forces for the next one. Im generally in a constant state of warfare, with just short interludes of peace.
I always play custom races, because I like to try different combinations of abilities, but I also like to fiddle around with them instead of using any of th prepackaged races. I usually create ones from various sci-fi that I've read/seen...and often use the Kzinti of course. Sentient species taste better...