Using a normal sized tea spoon (picture includes a 5p coin for scale) the following shows my normal dosage;
That is about 400mg as the scale shows. It should be noted that i take considerably less than some people but after taking the stuff most days of the week for a couple of years with maybe a couple of months off in between i've decided that this works a lot better for me that the 1 gram doses and larger that many people seem to favour.
For an attack dose i would suggest taking at least as much as 4 or 5 times this quantity. I haven't got a picture but i did try weighing out full completely level (not heaped) quantity with the same spoon and got a weight of 2.2 grams which could be fine as an attack dose for the first couple of days or so (you probably wouldn't feel much effect from it) then quickly tapering down to maybe 1 gram after a few days then dropping further from there once you really start to feel the effects.
If i was in your position (but with my low tolerance for the stuff) and i was taking this for the first time i would probably use;
Days one to four; two grams in the morning, 500mg at lunch
Days five to 2 weeks; one gram in the morning, 500mg at lunch
After 2 weeks; tapering fairly quickly down to 400mg in the morning, none at lunch.
This is just an estimate though, you need to experiment and see what works best for you. With this stuff less can definitely be more. The less you take the fewer side effects you get (like jitteriness, insomnia and stuff) but you still get pretty much all the good effects. Obviously there is a point where taking less just gives you less but for me the sweet spot is 400mg. Just because it seems to be working well for you doesn't mean it wouldn't work better if you took less.
One final but VERY IMPORTANT point; Before you leap in with the high attack doses, try a single dose of 400mg in the morning just to make sure you don't turn out to be extra sensitive to the stuff. If you start with 2 grams or more sods law states you'll turn out to be extra sensitive and you'll start feeling like someone spiked you with something half an hour after you get to work. Also, I've never heard of anyone being allergic to this stuff but that doesn't mean it wouldn't be possible. Start with a very low dose of this stuff before you start it properly with an attack dose just to be sure.
Also please do post an update once you find out if you like the stuff; I'd be very interested to hear how you get on.