The advice people have given you on GregTech really should be repeated: ALWAYS check NEI. Greg changes his recipes around very, very frequently, and his website is quite often out of date, and missing changed recipes. (A personal example: you used to be able to make double the RE-batteries by swapping out redstone for lead and sulfur. Now you need lead and sulfuric acid.)
Also, if you're familiar with IC2, you can replace redstone with electrum (silver + gold) to double your circuits. Actually, GT can be summarized as: Quantum Armor is ridiculous, let's make the journey there proportionally ridiculous! It's IC2's 'endgame extended.'
Some more specific pointers:
Weird pearly white ore: it's iridium ore. Save it for when you can silk touch and industrial macerate it, you'll need some to make a matter fabricator.
Keep in mind that the Mindcrack pack is designed for the players of a server called Mindcrack. It is meant to be difficult, complicated, and long; further, members of that server can set up chunk loaders and have their matter fabricators and quarries chug along, and so the costs for various things are set accordingly.
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In the Mindcrack default configuration, Gregtech's config will modify many IC2 (and some other mod) recipes to be more expensive, and require things from each other. Making most metal and diamond blocks requires a compressor. Making mixed metal ingots requires a Rolling Machine from Railcraft. The macerator will now require diamonds (although not TE's pulverizer, oddly) to make. Both IC2 Miners and BC Quarries require diamond drills. The electric tools will require steel. Matter Fabricators are both harder to make and require 100 times the energy. And, most IC2 'set and forget' generators require more exotic materials. (More on that in a bit.)
You can change the configuration - and Ultimate will use a different configuration that doesn't do this messing about with recipes - but there is honestly a lot you need to do in the config files to achieve this. I'd love for someone to set up a 'standardized' set of configs, one for each difficulty, but no such thing has emerged yet.
Greg's machines will also explode VIOLENTLY when given too much energy per packet - that is, do NOT attach them to the wrong voltage - where VIOLENTLY means 'sends out packets of increasing size to your cables, blowing out everything on the same network.' Also, taking apart a machine which is still working: explosion! As well, a handful of machines (The industrial grinder, the i. blast furnace, and the i. electrolyzer) have no energy storage, and will lose progress while eating energy if they aren't given enough every tick, which is a pain in the neck. Once again, NEI research is critical.
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The GregTech 'tiers', so to speak, can be roughly organized in terms of materials.
After a lot of iron mining, you'll have enough iron to make an Industrial Blast Furnace. (Alternatively, you could venture into the Nether, get a bunch of soul sand, nether bricks, and magma creams, and make a Railcraft Blast Furnace - and you probably will, eventually.)
Either blast furnace will allow you to cook iron into steel. Railcraft's furnace is painfully slow, but you can use charcoal in it, while the Industrial Blast Furnace requires coal dust, as in actual coal. You can use your steel to make tools, including the classic Drill and the essential Electric Wrench.
Both furnaces can also process aluminium into ingots, and Greg's furnace also lets you make silicon plates for solar panels.
About the same time, you'll probably want to set up the Industrial Grinder, which is like the pulverizer in that you get double ores plus some small bonuses, but is almost always strictly better than any other option. Still, shop around- Factorization, for instance, gives better yields for diamonds and coal, even though you need a diamond block and a stack and change of lead and silver each to set up shop.
Set up your Industrial Electrolyzer to move on to titanium: mine under forest-like biomes to get bauxite, electrolyze it to get tiny bits of titanium. Improve your Industrial Blast Furnace with steel a bit, then stick it in. You now have titanium for your precious Diamond Drill! You can now mine and quarry automatically. More importantly, you can make the Electric Rock Cutter, an electric Silk Touch tool to feed your precious stuff into the Grinder. At this point, try to Silk Touch that weird pearly white ore you might have seen wandering around - if you tried using NEI's hint function to reveal what it is, that's iridium ore, and you'll need at least one iridium plate (that's 4 iridium ingots) to make the matter fabricator.
Get some ruby. Like, a lot of ruby. Grind it up, process it, and you get chrome. Use the chrome, titanium, an iridium plate (look up the Implosion Compressor), and more to make your very first matter fabricator. And so on. Yes, it's painfully slow and expensive, but you can find weird ores in the End which produce a little iridium and are more abundant than Iridium Ore.
If you're a real glutton for punishment (or on a large server), you might try going for a lightning rod, and eventually a fusion reactor - hugely expensive, in terms of iridium and chrome, but hugely powerful.
(Wow, this is getting long.)
TL;DR: Gregtech makes the ridiculous IC2 endgame much, much harder to get to. Given how ridiculous Quantum Armor is, this might not be entirely unjustified. However, he messes with quite a few other mods to achieve this, like BC quarries, and people complain about this a lot.
Edit: Oh yeah, before I forget. A number of the machines are multiblocks: Of the ones I mentioned just now, the Industrial Grinder and Industrial Blast Furnace (And the railcraft blast furnace) are multiblocks. Also, what you can do with the Industrial Blast Furnace depends on which machine casings you use - look up Greg's website for info. (Weirdly, he doesn't list the refined iron recipe for standard machine casings...)
Fact of the day: on default configs, matter fabricating enough iridium for one plate costs about 467 MILLION EU.