Tried several very-low likeness demigod games. My general strategy:
0. Rush tech before turn 75. If you have gold mine, mine it ASAP.
1. Either rush the Oracle or he Great Lighthouse by all means, build both if possible. Stonehenge is very favorable too.
2. Expand overseas ASAP.
3. Found one religion or control at least 1 holy city.
4. Choose city sites carefully, AI tends to cram their cities, and we tend to make all our 10-15 cities metropolis (except the 2nd one, in case of rushing tech or wonder)
5. Adopt pacifism with Shwedagon Paya, for upkeep cost and GP rate. For early expansion, serfdom via Stonehenge is good too.
The most powerful civs in 3000 BC start are:
1. Greeks
The best UP, +150% GP rate, overpowered! And they usually starts near water, with many seafoods. Their tech rate is good too.
2. Incan
Mountain plot give gold and hammer, and terrace adds culture; and Quechua warrior needs no tech and bronze/iron, 5 power melee with +50% to archer, smashes any ancient units except normal axeman.
3. Chinese
UP is just fine, but usually has very good starting position.
4. Romans
Very good UP and UU, but the most important thing is that they have the best work rate: 3 turns a road even in 3000BC start. But war is usually not favorable in RAND, because AI city sites usually sucks, and war in classical age can bring down your economy and tech greatly. And also, it's hard to decide when to tech iron working. I always want to rush the Oracle and GL first, and by the time I build my legion, AI usually already have formidable defense.
5. Aztecs
UB good for slavery (I just won a game with them), UP is good to (although I didn't fight many wars, I even didn't fight barbs), work rate and tech rate also OK.
The worst civ in 3000BC start:
1. Americans
5 turns a road and twice of tech cost compared to other civs! UP not working in ancient times too.
2. Mali
Although they have good UP, UB and nice UU, the work rate is too damn bad, 6 turns a road!
3. Babylonian
Usually starts in desert, and no good UB and UU, UP is also not that good if you don't have many wars.