G'day Beerbelly84,
What else have you brewed so far? How did you go with those? What style of beer are you looking for? What ABV % are you looking for?
When I was just doing extract brewing, I used mainly Coopers international series kits (Pale Ale, Mex Cerv, English Bitter) & ended up not using anything else other than the Coopers Light Dried Malt.
The ferment process is the same - as in you do not add more suger a week later etc...
I used 1kg of Coopers Light Dried Malt (LDM) with each of these kits & filled the fermenter to anywhere between 18 - 22 litres ... so with an 18 litre brew you will get around 5.3% & about 4.4% with 22 litres.
Adding 500gms to that will up the ABV (Alcohol By Volume) by about 1.2%
Using the LDM is going to give you a fuller bodied beer that just using plain sugars like dextrose.
Other brewing tips (if you haven't picked them up already) are:
* Use a hydrometer to measure the specific gravity before pitching the yeast, and then one or two weeks later when you expect fermentation to be complete - record these values and use an online tool to determine what the ABV is.
* Use the hydrometer to determine that fermentation has finished - a stable reading 2 - 3 days in a row at a final gravity value in the range that you should expect for a finished beer indicates finished fermentation
* Get IanH's spreadsheet & play around with that -
http://www.aussiehomebrewer.com/forum/inde...st&p=736560
* Ferment your ales at 18-20 degrees celcius
Without knowing a bit more about what you are intereseted in achieving & how much experience you have I'll stop at that ... see how you go
PS: As Brewer Pete said too, most people on here are more interested in the taste and quality of what they brew than the alcohol volume ... and that is not to say that you aren't interested in that too, it's just that it isn't a priority for most & you may expect some "less than positive" responses to a question such as yours. Whatever your tase is, if you persist with it and take the advice of some of the homebrew veterans on this site you will move from brewing average, ok & good beer, to brewing great beer!
Cheers.