Im looking into the same thing. So far ive mostly used gasoline with Diesel generators however then you have to look for oil ALL of the time since you will quite quickly run ut, especially when you venture into 512 volt tier. I tried steam into methanol system as it gives to little energy per time for the amount of machines it requires. Im not a very big fan of steam as i think the tree farm into charcoal and RC boiler has been done to death several years ago.
I did find out that you can start making nuclear very quickly. I think its possible to do the basic reactors in LV era. So what im thinking is to make 1-2 full sized uranium 235 reactors that produces 200-300 eu/piece which you then connect to several CESU battery buffers which should be able to be converted into gregtech voltage (mfe requires HV autoclave
).
Actually not entirely sure how you convert IC2 EU to gregtech eu, i know it involves IC2 battery buffers and gregtech transformers but im not entirely sure how it really works out. For instance if i use CESU buffers could i either use 4 to produce 1 amp of 512 V or 1 CESU to produce 4 amp of 32 voltage? I haven't tried it so im not sure of the specifics.
As you progress into 512 you should be able to go into the more advanced fluid reactors where thorium really shines or MOX reactors to get into the 2048 voltage tier.
OFC this requires you to find a nice solid vein of galena ore and uranium ore which isn't all that easy to do unless you are lucky in the start.
When you can make 2048 stuff im going for the distillation tower to produce biogas from sheared leaves
1 leaf block to 1biochaff to 1 bucket of biomass to 32 buckets of biogas with a net gain of about 500000-600000 eu